The Communication Architecture is a strategy for connecting host computers and other communicating equipment. It defines necessary elements for data communication between devices. The communication architecture therefore, defines a standard for the communicating hosts. A programmer formats data in a manner defined by the communication architecture and passes it on to the communication software. Separating communication functions adds flexibility, for example, we do not need to modify the entire host software to include more communication devices.Layer Architecture
Layer architecture simplifies the network design. It is easy to debug network applications in a layered architecture network. The network management is easier due to the layered architecture. A complex problem is divided into a number of pieces of manageable and comprehensible size. It provides structured modular approach. Each module can be developed and tested independently. It allows easy enhancement and implementation of the functions of a particular layer without affecting other layers. Network layers follow a set of rules, called protocol. The protocol defines the format of the data being exchanged, and the control and timing for the handshake between layers.Some of the basic principles followed in Layering:
# Use optimum number of layers. # Put similar functions in the same layer. # Create a layer where there is need for different levels of abstraction. # Allow changes of functions to be made with in a layer without affecting others. # Create layer boundaries for each layer with its upper and lower layers. # Choose layer boundaries to minimize information flow across the boundaries.Open Systems Interconnection (OSI) Model
International standard organization (ISO) established a committee in 1977 to dev elop the architecture for computer communication. Open Systems Interconnection (OSI) reference model is the result of this effort. In 1984, the Open Systems Interconnection (OSI) reference model was approved as an international standard for communications architecture. The term “open” denotes the ability to connect any two systems which conform to the reference model and associated standards. The OSI model is now considered the primary Architectural model for inter-computer communications. The OSI model describes how information or data makes its way from application programs (such as spreadsheets) through a network medium (such as wire) to another application program located on another network. The OSI reference model divides the problem of moving information between computers over a network medium into SEVEN smaller and more manageable problems. This separation into smaller more manageable functions is known as layering.
The process of breaking up the functions or tasks of networking into layers reduces complexity. Each layer provides a service to the layer above it in the protocol specification. Each layer communicates with the same layer's software or hardware on other computers. The lower 4 layers (transport, network, data link and physical-Layers 4, 3, 2, and 1) are concerned with the flow of data from end to end through the network. The upper four layers of the OSI model (application, presentation and session-Layers 7, 6 and 5) are orientated more toward services to the applications. Data is encapsulated with the necessary protocol information as it moves down the layers before network transit.Physical Layer
Physical layer provides physical interface for transmission of information. It defines rules by which bits are passed from one system to another on a physical communication medium. This layer covers all mechanical, electrical, functional and procedural aspects for physical communication. Such characteristics as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other similar attributes are defined by physical layer spec ifications. Devices working on at physical layer are hubs, repeaters, cables, modems etc.Data Link Layer
Data link layer attempts to provide reliable communication over the physical layer interface. It breaks the outgoing data into frames and reassembles the received frames. Data link layer create and detect frame boundaries. It handles errors by implementing an acknowledgement and retransmission scheme. It implements flow control, supports points-to-point as well as broadcast communication. This layer also supports simplex, half-duplex or full-duplex communication.Network Layer
Network Layer implements routing of frames (packets) through the network. This layer defines the most optimum path the packet should take from the source to the destination. It also defines logical addressing so that any endpoint can be identified. This layer handles congestion (crowding or jamming) in the network, facilitates interconnection between various networks (Internetworking). The network layer also defines how to fragment a packet into smaller packets to accommodate different media. Device working on Network layer is router.Transport Layer
Purpose of this layer is to provide a reliable mechanism for the exchange of data between two processes in different computers. This layer ensures that the data units are delivered error free, data units are delivered in sequence and there is no loss or duplication of data units. It provides connectionless or connection oriented service. This layer also provides the connection management and multiplex multiple connection over a single channel. It is also called as the heart of the OSI layers.Session Layer
Session layer provides mechanism for controlling the dialogue between the two end systems. It defines how to start, control and end conversations (called sessions) between applications. This layer requests for a logical connection to be established on an end-user’s request. Any necessary log-on or password validation is also handled by this layer. Session layer is also responsible for terminating the connection. This layer provides services like dialogue discipline which can be full duplex or half duplex. Session layer can also provide check-pointing mechanism such that if a failure of some sort occurs between checkpoints, all data can be retransmitted from the last checkpoint.Presentation Layer
Presentation layer defines the format in which the data is to be exchanged between the two communicating entities. Presentation layer is responsible for converting data into standard format. Examples: ASCII, JPEG, MPEG, BMP, WAV, MP3 etc.Computer Networks
It also handles data encoding - data decoding, data compression data - decompression and data encryption - data decryption (cryptography).Application Layer
Application layer interacts with application programs and is the highest level of OSI model. Application layer contains management functions to support distributed applications. Examples of application layer are applications such as file transfer, electronic mail, remote login etc. Application layer is responsible for providing network services to user. It is also known as desktop layer. Here identification of services is done using port numbers. Ports are nothing but sockets i.e. entry and exit point to the layer.OSI in Action
A message begins at the top application layer and moves down the OSI layers to the bottom physical layer. As the message descends, each successive OSI model layer adds a header to it. A header is layerspecific information that basically explains what functions the layer carried out. Conversely, at the receiving end, headers are striped from the message as it travels up the corresponding layers.


In production from January 1983 to November 1993, the Apple IIe remained relatively unchanged through the years. However there was one significant motherboard update, a major firmware update, two cosmetically revised machines and an official compatibility solution from Apple, in the form of an LC PDS card for certain models of the Macintosh computer line, known as the Apple IIe Card. These revisions are detailed below.
The Revision A motherboard: At the time of the Apple IIe's introduction, and well into the first few months of production, this motherboard shipped with all units. Graphics modes supported are identical, and limited to, that of the Apple II Plus before it. The logic board is not compatible with the ROM based firmware update (introduced some years later) and most newer plug in expansion slot cards.
The Revision B motherboard: Shortly after the Revision A motherboard's release in 1983, engineers discovered that the bank-switching feature (which used a paralleled 64 KB of RAM on the Extended 80 Columns Card; or 1 KB to produce 80 columns using bank-switching) could also be used to produce a new graphics mode, Double-High-Resolution, with doubles the horizontal resolution and increases the number of colors from the 6 of standard High-Resolution to 15. In order to support this, some modifications had to be made to the motherboard, which became the Revision B. In addition to supporting Double-High-Resolution and a rarely used Double-Low-Resolution mode it also added a special video signal accessible in slot-7.
Apple upgraded the motherboard free of charge. In later years Apple labeled newer IIe motherboards with a A suffix once again, although in functionality they were Revision B motherboards.
New case and keyboard: In 1984, Apple revised the case and keyboard. The original IIe uses a case very similar to the Apple II Plus, painted and with Velcro-type clips to secure the lid with a strip of metal mesh along the edge to eliminate radio frequency interference. The new case is made of dyed plastic mold in a slightly darker beige with a simplified snap-case lid. The other noticeable change is a new keyboard, with more professional looking print on darker keycaps (small black lettering, versus large white print). This was the first cosmetic change.
The Enhanced IIe: In March 1985, Apple replaced the original machine with a new revision called the Enhanced IIe. It is completely identical to the previous machine except for 4 chips changed on the motherboard (and a small Enhanced or 65C02 sticker placed over the keyboard power indicator). The purpose of the update was to make the Apple IIe more compatible with the "Apple IIc
" (released the previous year) and in some respects to a smaller degree, the "Apple II Plus". This change involved a new processor, the CMOS based 65C02 CPU, a new character ROM for the text modes, and two new ROM firmware chips. The 65C02 added more CPU instructions, the new character ROM added 32 special MouseText characters (which allowed the creation of a GUI-like display in text mode, similar to IBM code page 437), and the new ROM firmware fixed problems and speed issues with 80 columns text, introduced the ability to use lowercase in Applesoft BASIC and Monitor, and contained some other smaller improvements (and fixes) in the latter two (including the return of the Mini-Assembler—which had vanished with the introduction of the II Plus firmware).
Although it affected compatibility with a small number of software titles (particularly those that did not follow Apple programming guidelines and rules, used illegal opcodes that were no longer available in the new CPU, or used the alternate 80-column character set that MouseText now occupied) a fair bit of newer software — mostly productivity applications and utilities — required the Enhancement chipset to run at all. An official upgrade kit, consisting of these four replacement chips and an Enhanced sticker badge, was made available for purchase to owners of the original Apple IIe. An alternative at the time, which some users choose as a cost-cutting measure, was to simply purchase their own 65C02 CPU and create (unlicensed and illegal) duplicates of the updated ROMs using re-rewritable EPROM chips. When Apple phased out the Enhancement kit in the early 1990s, this became the only available method for users looking to upgrade their IIe, and remains so right up until present day. An Enhanced machine identifies itself with the name Apple IIe on its start up splash screen (as opposed to the less specific Apple II).
The Platinum IIe: In January 1987 came the final revision of the Apple IIe, often referred to as the Platinum IIe, due to the color change of its case to the light-grey color scheme that Apple dubbed Platinum. Changes to this revision were mostly cosmetic to modernize the look of the machine. Besides the color change, there was a new keyboard layout with built-in numeric keypad. The keyboard was changed to match the layout of the Apple IIGS, with the reset key moved above the ESC and '1' keys, the Open and Solid Apple modifier keys replaced by Command and Option and the power LED relocated above the numeric keypad. Gone were the recessed metal ID badges (showing the Apple logo and name, with IIe beside it) replaced with a simpler Apple IIe silk screened on the case lid in the Apple Garamond font. A smaller Apple logo badge remained, which was moved to the right side of the case.
Internally, a (reduced in size) Extended 80 Columns Card was factory pre-installed, making it come standard with 128 KB RAM and Double-Hi-Res graphics enabled. The motherboard has a reduced chip count by merging the two system ROM chips into one and used higher density memory chips so its 64 KB RAM could be made up of two (64 Kbx4) chips rather than eight (64 Kbx1) chips, bringing the count down to a total of 24 chips. A solder pad location on the motherboard, present since the original IIe, for (optionally) making presses of the "Shift
" keys detectable in software, is now shorted by default so that the feature is always active. Next, in a move to reduce radio frequency interference when a joystick plugs into the motherboard's Game I/O socket, filtering capacitors were added. While this made no difference to the average user, it had the negative effect of lowering the available bandwidth to the socket, which is often used by specialized devices for such purposes as measuring temperature, controlling a robotic device, or even simplistic networking for data transfer to another computer. In such cases the specialized devices were rendered useless on the Platinum IIe unless the user removed the capacitors from the board.
There were no firmware changes present, and functionally the motherboard is otherwise identical to the Enhanced IIe. This final model of the Apple IIe was discontinued in November 15, 1993; officially retiring the entire Apple II family line with it.
International versions: The Apple IIe keyboard differed depending on what region of the world it was sold in. Sometimes the differences were very minor, such as extra local language characters and symbols printed on certain keycaps (e.g. French accented characters on Canadian IIe, or the British Pound symbol on the UK IIe) while other times the layout and shape of keys greatly differed (e.g. European IIe). In order to access the local character set and keyboard layout, a user-accessible switch is found on the underside of the keyboard — flipping it will instantly switch the video output and keyboard input from the US character set to the local set. To support this, special double capacity video and keyboard ROMs are used; in early motherboards they had to reside on a tiny circuit card that plugged into the socket. In some countries these localized IIe's also support 50 Hz PAL video instead of the standard 60 Hz NTSC video and the different 220/240 volt power of that region. An equivalent of the "PAL color card" for the earlier Apple II europlus model was integrated into the motherboard of these IIes, so that color graphics are available without the addition of a slot card.
Another difference with the European IIe, is the Auxiliary slot physically moved in location so it is in line and in front of slot-3, preventing both slots from being used simultaneously for full-sized cards. A few third-party cards are affected by this: some European cards plug into both slots simultaneously and are thus unusable on American IIes, and some American cards that do not fit into the case of European IIes because the European location of the Auxiliary slot leaves less room for them.


What You Will Learn
As data centers consolidate into more complex systems, they take advantage of new speed increases and technologies. The speed changes from 1- to 10-Gbps infrastructure were easy to understand. With speeds in the data center now increasing from 10 Gbps to 40 Gbps and eventually to 100 Gbps, different optical technologies and cabling infrastructure are required. This document introduces the cable requirements for 40-Gbps infrastructure and fundamental cabling principles supporting Cisco Nexus® 9000 Series Switches. Although alternative cabling options are mentioned (Twinax and active optical assemblies), the main focus of the document is cabling for pluggable optical Enhanced Quad Small Form-Factor Pluggable (QSFP+) modules.
The new Cisco Nexus 9000 Series provides high 1-, 10-, 40-, and (future) 100-Gbps Ethernet densities with outstanding performance and a comprehensive feature set. The Cisco Nexus 9000 Series provides a versatile platform that can be deployed in multiple scenarios - direct-attach 1-, 10-, and 40-Gbps access and collapsed aggregation and access deployments, leaf-and-spine architecture, and compact aggregation solutions.
Structured (Semi-permanent Links) or Unstructured System
When designing a networking system, it is important to plan the cabling system in advance. The goal is to address current network requirements as well as accommodate future growth. A structured cabling system provides a flexible cabling plan to address the commonly performed tasks of moving, adding, and changing the infrastructure as the network grows. A good analogy for a structured cabling system is the electrical wiring in your home. When connecting appliances and devices, you require only a 5-foot connection to the closest electrical outlet. However, without an electrical outlet, all appliances would have to connect directly to the breaker or panel, requiring a cable of 200 feet or more. This approach would be inefficient and would become unmanageable as you add multiple appliances and devices throughout the home. The structured wiring is those permanent wires in the walls and ceilings to electrical outlets throughout your home. The same concept applies to data centers with the deployment of robust cabling links between two patch panels (similar to the outlets in the wiring example). Structured cabling becomes a necessity as the infrastructure grows and as constant moves and changes reinforce the need for a reliable network that is also easy to troubleshoot.
Structured cabling requires additional initial investment to create the cabling infrastructure, but the recurring benefits more than outweigh the slight additional incremental cost. Imagine the cost of deploying a two-fiber optical jumper each time a new server is placed in the data center. Further, regardless of whether the data center has a raised floor or uses overhead cabling, both result in time-consuming and inefficient deployment in an unstructured environment. Likewise, management of such an environment is cumbersome, increasing the risk of outages caused by human errors.
Structured cabling uses fiber termination connector panels that are connected through permanent links of optical cabling, typically configured in a star topology. All cabling in the data center coming from the server area is consolidated in a central location near the core, aggregation-layer, or spine switch in the network (analogous to the breaker or power panel in the home electrical system analogy). The permanent pre-terminated trunk cables branch to the zones in the data center, which contain servers, storage, or network devices. Note that with structured cabling, you still need some device-to-device connections at the access layer. As you can see in Figure 1, when you make these short connections within the same cabinet or even a few cabinets away, patch panels may not be required. Likewise, patch panels would not be required for inter-switch link connections.
Figure 1. Structured Cabling with Patch Panels
Unstructured cabling occurs when optical links are deployed point to point or device to device with no patch panels installed in the link. In this situation, cabling pathways become congested with an entangled mess of two-fiber optical patch cords (Figure 2). Likewise, routing new patch cords in ceiling or floor trays all the way across a data center each time a new device is deployed is extremely inefficient.
Figure 2. Unstructured Cabling
Types of Fiber Optic Fiber
As a result of the emergence of high-data-rate systems such as 10, 40, and 100 Gigabit Ethernet, laser-optimized multimode fiber (MMF) has become the dominant fiber choice. These 50-micron fibers are optimized for the 850-nanometer (nm) transmission of vertical-cavity surface-emitting laser (VCSEL)-based transceivers. The TIA-492AAAC OM3 detailed fiber standard was released in March 2002, and the TIA-492AAAD OM4 detailed fiber standard was released in August 2009. Corning Cable Systems suggests installing either OM3 or OM4 cabling in the data center space depending on length requirements. The two fibers have different bandwidths (information carrying capacity), which results in different achievable lengths for the same transceivers. Table 1 shows the achievable distances based on the OM3 and OM4 fibers at various data rates. TIA 942-A Telecommunication Infrastructure Standards for Data Centers recognizes only the OM3 and OM4 MMF types (it removed OM1, which was 62.5 microns, and OM2, which was the standard 50 microns). The standard also provides guidance to recommended OM4 cables using LC and MTP connectivity.
Table 1. 850-nm Ethernet Distance (m)
OM3 (50 microns)
• 2 fibers
• 2 fibers
• 2 fibers
• 8 fibers
• 8 fibers
OM4 (50 microns)
• 2 fibers
• 2 fibers
• 2 fibers
• 8 fibers
• 8 fibers
Types of Optical Transceiver Modules
The transceiver is an electronic device that receives an electrical signal, converts it into a light signal, and launches the signal into a fiber. It also receives the light signal, from another transceiver, and converts it into an electrical signal. For data rates greater than or equal to 1 Gbps, a multimode transceiver uses an 850-nm VCSEL transceiver.
SFP+ is the dominant transceiver form factor used for 1 and 10 Gigabit Ethernet applications. The transceiver uses an LC optical connector interface. For more information, see http://www.cisco.com/en/US/prod/collateral/modules/ps5455/data_sheet_c78-455693.html.
The QSFP+ transceiver is the dominant transceiver form factor used for 40 Gigabit Ethernet applications. In 2010 the IEEE standard 802.3ba released several 40-Gbps based solutions, including a 40GBASE-SR4 parallel optics solution for MMF. Since then, several engineered solutions have been released, including 40GBASE-CSR4, which is similar to 40GBASE-SR4 but extends the distance capabilities. Another solution released by Cisco is a bidirectional 40-Gbps transceiver that uses a two-fiber LC optical interface. For more information, see http://www.cisco.com/en/US/prod/collateral/modules/ps5455/data_sheet_c78-660083.html.
Table 2 summarizes the differences between QSFP transceiver optical interfaces and electrical interfaces. Table 3 summarizes the connectivity options.
Table 2. Comparison of QSFP Transceiver Optical Interface and Electrical Interface
Electrical and Optical Lanes Diagram
Parallel optical transceivers used for 40GBASE-SR4 and 40GBASE-CSR4 have 10-Gbps electrical lanes that are mirrored in the optical outputs and thus require eight fibers with an MTP connector interface. Each fiber either transmits (Tx) or receives (Rx) 10-Gbps traffic at a single wavelength.
Bidirectional optical transceivers used for 40GBASE-SR-BD use the same 10-Gbps electrical lanes, which are then combined in the optical outputs, thus requiring two fibers with an LC connector interface. Each fiber simultaneously transmits and receives 20-Gbps traffic at two different wavelengths.
Table 3. Connectivity Options
Pluggable optical modules
Allows extended-reach capabilities (up to 400m on MMF and 10 km on single mode fiber [SMF]); cable links and optical engines are separate and thus can be upgraded independently
More expensive than other short-reach direct-attach options
Passive and active direct-attach copper
• SFP-H10GB-CU2M QSFP-H10G-ACU7M
Allows lower-cost short-reach capability; typically used for top-of-rack (ToR)-to-server connectivity
Limited to 5m (passive) to 10m (active), and coaxial cable can be stiff and bulky in high-density deployments
Active optical cable (AOC) assemblies
QSFP+-AOC (1, 2, 3, 5, 7, and 10m)
Allows lower-cost short-reach capability with more flexible cabling; typically used for ToR-to-server connectivity
Limited to less than 10m; reconfigurations of length or failed transceiver requires replacement of entire assembly
Typical Optical Cabling Components
Table 4 provides an overview of typical cabling components. These components will be mentioned in the cabling discussions throughout the remainder of this document.
Table 4. Typical Cabling Components
MTP trunk cable
These fiber trunk cables are typically 12 to 144 fibers and create the permanent fiber links between patch panels in a structured environment. They are pre-terminated from the manufacturer with MTP connectors at a specified length and have a pulling grip for easy installation.
The connector housings are physically mounted in a 19-inch rack or cabinet. They are typically offered in various sizes such as 1 rack unit (1RU), 2RU, or 4RU, which refers to the amount of rack space required for mounting.
The MTP-LC module is installed in the connector housings. The module breaks out the MTP connections from the trunk cables to LC connections for 1- and 10-Gbps applications. The trunk cables plug into the rear MTP of the module, and the LC jumpers plug into the front of the module.
MTP connector panel
The MTP-MTP connector panel (sometimes called the bulkhead) is installed in the housings. It offers a connection point between the MTP trunk and the MTP jumper for 40- and 100-Gbps applications. The trunk cables plug into the rear of the panel, and the MTP jumpers plug into the front of the panel.
2x3 conversion module
The 2x3 conversion module is used for 4-channel (8-fiber) parallel optics applications, such as 40GBASE-SR4. It allows 100% utilization of trunk cables by converting a pair of 12-fiber MTP connections into three 8-fiber MTP connections. The trunk cables plug into the rear MTP of the module, and the MTP jumpers plug into the front of the module to make the connection to the switch.
LC or MTP jumpers
The LC or MTP jumpers create the connection between the device port and the structured cabling through the connector panel.
Learn more about each of these products in the Corning product catalog; see "Indoor Preterminated Systems" at http://catalog.corning.com/CableSystems/en-US/Default.aspx.
Cisco Nexus 9000 Series Architecture
Today data centers are facing unprecedented requirements for performance, scalability, and agility as virtualization, application workload distribution and mobility, and cloud and big data applications are becoming the main factors influencing data center operation. The Cisco Nexus 9000 Series consists of the Cisco Nexus 9500 platform modular switches and the Cisco Nexus 9300 platform fixed-port switches (Table 5). It provides the next-generation solution to overcome these data center challenges with a high-performance, low cost, flexible and agile application centric infrastructure.
Table 5. Cisco Nexus 9000 Series Switches
Cisco Nexus 9500 platform
The Cisco Nexus 9500 platform consists of modular switches. The Cisco Nexus 9508 Switch is the first switch released for this platform. With more than 30 terabits per second (Tbps) of backplane bandwidth, the switch supports 1, 10, 40, and (future) 100 Gigabit Ethernet interfaces through a comprehensive selection of modular line cards. Configurable with up to 1152 10 Gigabit Ethernet or 288 40 Gigabit Ethernet ports, the switch provides sufficient capacity for both access- and aggregation-layer deployments.
Cisco Nexus 9396PX Switch
The Cisco Nexus 9300 platform consists of fixed-port switches designed for ToR and middle-of-row (MoR) deployment in data centers. The Cisco Nexus 9396PX is a 2RU non-blocking Layer 2 and 3 switch with 48 1- and 10-Gbps SFP+ ports and 12 40-Gbps QSFP+ ports.
Cisco Nexus 93128TX Switch
The Cisco Nexus 9300 platform consists of fixed-port switches designed for ToR and MoR deployment in data centers. The Cisco Nexus 93128TX is a 3RU 1.28-Tbps Layer 2 and 3 switch with 96 1/10GBASE-T ports and 8 40-Gbps QSFP+ ports.
Cisco Nexus 9000 Series Switches can run in two operating modes: the standard Cisco Nexus device mode with enhanced Cisco NX-OS Software as the operating system, or the Cisco Application Centric Infrastructure (ACI) mode to take full advantage of an automated policy-based approach to system management.
While operating in the standard Cisco Nexus device mode, Cisco Nexus 9000 Series Switches can be deployed in a variety of data center network designs. Cisco Nexus 9500 platform switches, with their high-density line-rate 40-Gbps line cards, can be placed at the aggregation layer to provide aggregated 40-Gbps connectivity for the access switches. Cisco Nexus 9500 platform switches, with their 1- and 10-Gbps line cards, can be deployed as high-performance access-layer end-of-row (EoR) or MoR switches for 1- and 10-Gbps server connectivity. Cisco Nexus 9300 platform switches are well designed for the access layer as ToR switches. The Cisco Nexus 93128TX is also a good choice as a MoR access switch.
As shown in Figure 3, Cisco Nexus 9500 and 9300 platform switches are deployed in the traditional three-tier design. The Cisco Nexus 9500 platform switches are placed at the core aggregation tiers, and the Cisco Nexus 9500 or 9300 platform switches are deployed at the access tier.
Figure 3. Traditional Three-Tier Design
Cisco Nexus 9500 and 9300 platform switches both support Cisco Nexus 2000 Series Fabric Extenders (FEXs). By using the Cisco Nexus 2000 Series, Cisco Nexus 9500 and 9300 platform switches can build a cost-effective and scalable collapsed aggregation and access layer for 1- and 10-Gbps server connectivity with 40-Gbps uplinks to the network. Figures 4 and 5 show Cisco Nexus 9500 and 9300 platform switches, respectively, in this collapsed two-tier design.
Figure 4. Cisco Nexus 9500 Platform Switches and Fabric Extenders for Collapsed Aggregation and Access Layer
Figure 5. Cisco Nexus 9300 Platform Switches and Fabric Extenders for Collapsed Aggregation and Access Layer
Modern data center applications, such as big data and high-frequency trading (HFT) applications, and virtualized and clustered environments have shifted the data center traffic load from north-south client-server traffic to east-west server-to-server traffic. Data center architects are starting to gravitate to the spine-leaf topology, which flattens the network to two tiers and increases traffic-forwarding efficiency for the increasing amount of east-west traffic. With their non-blocking architecture and high 10- and 40-Gbps port densities, the Cisco Nexus 9500 and 9300 platforms are excellent choices for a spine-and-leaf network design. Figure 6 shows a sample spine-and-leaf network constructed with Cisco Nexus 9500 and 9300 platform switches. With their versatile line-card options, Cisco Nexus 9500 platform switches can be deployed at both the spine and leaf layers.
Figure 6. Cisco Nexus 9500 and 9300 Platforms for Spine-and-Leaf Designs
All the preceding deployment scenarios use 1-, 10-, and 40-Gbps cabling for physical connectivity. 1- and 10-Gbps cabling infrastructure is well understood and commonly deployed, but 40-Gbps cabling remains a new challenge to data center operators because of its different transceiver technologies and cabling requirements. The rest of this document provides guidance and options for 40-Gbps fiber cabling designs.
Cabling Options for 40-Gbps Two-Fiber Bidirectional Optics (QSFP-40G-SR-BD)
Since the introduction of 40 Gigabit Ethernet with the IEEE 802.3ba standard in 2010, the only multimode solution on the market has used parallel optics. The parallel optics solution, 40GBASE-SR4, uses eight fibers to transmit four duplex channels each using 10 Gigabit Ethernet. This solution allows an economical path to 40 Gigabit Ethernet data rates, while using many of components of 10 Gigabit Ethernet market solutions.
The change from two-fiber serial transmission to parallel transmission required some changes in the cabling. First, the connector type was converted from the traditional 2-fiber LC duplex connector to a 12-fiber MTP connector. This change created some new challenges: in particular, with the pinning and polarity of the connector. The traditional LC duplex connector uses a ceramic ferrule on each connector, which is aligned in an adapter panel with the use of a ceramic alignment sleeve. However, the MTP connector uses a pinned and non-pinned connector alignment system, making it imperative to always maintain the correct pinning. Likewise, polarity correction of a 2-fiber system can be easily achieved by flipping the position of the LC connector in the duplex clip. However, correction of polarity in a 12-fiber MTP connector can be more challenging because all 12 fibers are in a single ferrule.
In response to these challenges, Cisco developed a two-fiber 40-Gbps Bidirectional (BiDi) multimode solution. This solution uses two different transmission windows (850 and 900 nm) that are transmitted bidirectionally over the same fiber. This approach allows the use of the same cabling infrastructure for 40 Gigabit Ethernet as was used for 1 and 10 Gigabit Ethernet. The pluggable bidirectional transceiver has the same QSFP+ format as the existing 40GBASE-SR4 transceivers. Therefore, the same switch line card with QSFP+ ports can support either parallel optics 40GBASE-SR4 or bidirectional optics 40GBASE-SR-BD solutions.
Thus, when directly connecting a 40 Gigabit Ethernet bidirectional transceiver to another bidirectional transceiver, a Type A-to-B standard LC duplex patch cord can be used. As defined in TIA-568-C.3, a Type A-to-B duplex patch cord is constructed with one (blue) fiber in connector position A on one end and in connector position B on the other end, and likewise for the second (orange) fiber, as shown in Figure 7. This reverse fiber positioning allows a signal to be directed from the transmit position on one end of the network to the receive position on the other end of the network.
Figure 7. Type A-to-B Jumper Fiber Mapping (per TIA-568-C.3)
This type of direct connectivity is suggested only within a given row of cabinets. The jumper assembly is tested only to the requirements of an interconnect cable, as defined in ANSI/ICEA S-83-596-2001. It has less robustness (less tensile strength, less crush and impact resistance, etc.) than a distribution-style trunk cable. Figure 8 depicts a situation in which two 40 Gigabit Ethernet bidirectional ports on two switches are directly linked using a Type A-to-B LC duplex jumper.
Figure 8. Direct Connection for 40 Gigabit Ethernet Bidirectional Transceiver
However, when considering structured cabling, you must consider deployment of more permanent links. The simplest structured cabling link includes a patch panel on both ends of the link, with a jumper assembly making the connection to the electronic ports. This type of cabling is called an interconnect, because both jumpers in the link connect from the structured cabling patch panel to the electronics ports. Figure 9 shows an interconnect link between two bidirectional ports installed in a switch. The link consists of an MTP-based trunk, MTP-LC modules, and LC jumpers. By installing the MMF MTP assembly, you can provide more scalability to accommodate future data rates that may require parallel optics for transmission. This future migration can be accomplished simply by changing the patch panels on each end of the link, without the need to disrupt the cabling infrastructure.
Figure 9. Interconnect for 40 Gigabit Ethernet Bidirectional Transceiver
The final cabling approach to consider is a cross-connect design, as shown in Figure 10. In this scenario, two separate structured cabling links connect the two switches through a centralized cross-connect. The advantage of this approach is that it allows the most flexible network configuration. The electronics can be placed in various locations throughout the data center, with structured cabling links between the cross-connect location and designated zone cabinets. When new equipment is installed, only patch cords are required to make the connection from the equipment to the patch panels. Moreover, any port-to-any port connectivity can be achieved at the cross-connect location. This connection is achieved in an orderly and manageable way, unlike what can occur with a direct connectivity scheme in which patch cord assemblies are used to make all port-to-port connections in the data center without structured cabling.
Figure 10. Cross-Connect for 40 Gigabit Ethernet Bidirectional Transceiver
Table 6 provides samples of the part numbers needed for the bidirectional cabling links.
Table 6. Sample of Part Numbers for Bidirectional Cabling Links
12-fiber LC duplex to MTP (pinned); OM3
LC uniboot OM3 jumper; 2m
24-fiber MTP OM3 trunk cable; 100 ft
Note: This example uses a 24-fiber trunk cable, but trunk cables can have 12 to 144 fibers at any length.
Cabling Options for 40-Gbps Parallel Optical Modules
As previously mentioned, in 2010 IEEE 802.3ba approved the 40GBASE-SR4 physical-medium-dependent (PMD) multimode parallel optic solution, which uses eight fibers to transmit four duplex channels each at 10 Gigabit Ethernet. As shown in Figure 11, each transceiver transmits over four fibers and also receives transmissions over four fibers.
Also as previously mentioned, parallel optics does require a change from traditional cabling methods, which requires learning and so creates an incentive to move to the bidirectional solution at 40 Gigabit Ethernet. The main advantage of the parallel optics transceiver over the bidirectional transceiver at 40 Gigabit Ethernet is reach. For example, if you cable your data center with OM3 fiber at 10 Gigabit Ethernet, you can support distances up to 300m. Then if you move to 40 Gigabit Ethernet, you can support the same 300m distance with the same OM3 fiber and a 40GBASE-CSR4 transceiver. However, if your cabling distances do not justify the extra distance capability, then the bidirectional solution would be used (Figure 11).
Figure 11. 40GBASE-SR4 and 40GBASE-cSR4 Lane Assignments
The dilemma is that MTP cable assemblies, which have been used for more than a decade for cabling in the data center, are built on 12-fiber position connectors. Thus, each link has four unused fibers. There are several basic cabling options for parallel optics connectivity. One approach is to ignore the unused fibers and continue to deploy 12 fibers. Another approach is to use a conversion device to convert two 12-fiber links into three 8-fiber links. Three solutions exist (summarized in Table 7 and Figure 12).
• Solution 1: The no-conversion scenario retains the whole 12-fiber based cabling system, but 33 percent of the fiber is not used. Additional cost is associated with the purchase of additional fiber, and your system includes unused fiber.
• Solution 2: This solution uses conversion modules to convert the unused fibers into useable optical links. For every two 12-fiber MTP connectors in the backbone cable, you can create three 8-fiber links. There is an additional cost for the additional MTP connectivity, but that is offset by the cost savings from 100 percent fiber utilization in the structured cabling. When you reuse existing deployed MTP cabling, you gain great value when you use the conversion module to use all previously deployed fiber, and you eliminate the cost of having to deploy additional cabling.
• Solution 3: This scenario uses standard MTP patch panels with a conversion assembly (two 12-fiber MTP connectors on one end going to three 8-fiber MTP connectors on the other end). This approach does not add any connectivity to the link, and it achieves full fiber utilization. However, although this approach may appear attractive, it involves considerable cabling challenges. For example, if you need only two 40-Gbps connections to a piece of equipment, what do you do with that third 8-fiber MTP connection? What if the 40-Gbps ports are in different chassis blades or completely different chassis switches? The result will be long assemblies, which will be difficult to manage in an organized way. For this reason, Solution 3 is expected to be the least desirable and so the least deployed method.
Table 7. Three Cabling Solutions for 40-Gbps Connectivity
Uses traditional 12-fiber MTP connectivity and ignores unused fiber
Simplicity and lowest link attenuation
Does not use 33% of the installed fiber, and thus requires more cable raceway congestion
Converts two 12-fiber links to three 8-fiber links through a conversion patch panel
Uses all backbone fiber and creates a clean, manageable patch panel with off-the-shelf components
Entails additional connectivity costs and attenuation associated with the conversion device
Converts two 12-fiber links to three 8-fiber links through a conversion assembly and standard MTP patch panels
Uses all backbone fiber with additional connectivity
Creates cabling challenges with dangling connectors and non-optimized-length patch cords that require customization
Figure 12. Cabling Solutions for 40-Gbps Connectivity
Corning offers components to build all three solutions. However, Corning suggests implementation of the conversion module solution, especially if you are using previously installed MTP trunks. This solution allows 100 percent fiber utilization while maintaining any port-to-any port patching. If you are installing all new cabling, then you could consider the no-conversion solution, assuming that the cable raceway is not a concern. Typically, the conversion harness is deployed only in specific applications, such as at the ToR switch, where 40-Gbps ports are in a close cluster and patching between blades in a chassis switch is not required.
When directly connecting a parallel optics 40 Gigabit Ethernet transceiver to another 40 Gigabit Ethernet transceiver, a Type-B pinless-pinless MTP jumper should be used. As shown in Figure 13, a Type-B MTP jumper assembly, as defined in TIA-568-C.3, has the blue fiber 1 assembled in connector position 1 on one end of the assembly, and this same fiber assembled in connector position 12 on the other end of the assembly. This reverse fiber positioning allows the signal to flow from transmission on one end of the link to reception on the other end.
Figure 13. Type-B Array Patch Cord (per TIA-568-C.3)
This type of direct connectivity is suggested only within a given row of cabinets. The jumper assembly is tested only to the requirements of an interconnect cable, as defined in ANSI/ICEA S-83-596-2001. It has less robustness (less tensile strength, less crush and impact resistance, etc.) than a distribution-style cable, which would be used for structured cabling trunks. Figure 14 shows two switch ports directly cabled with an MTP jumper patch cord.
Figure 14. Direct Connection for 40 Gigabit Ethernet Parallel Optic Transceiver
Similar to the bidirectional cabling approach, the most basic structured cabling solution is an interconnect. The only difference between an interconnect solution and parallel optics is that the connector type of the patch panels instead is MTP. Figure 15 shows several interconnect link scenarios with various patch-panel options. As previously discussed, the 2x3 conversion modules, depicted in Figure 15a, allow 100 percent fiber utilization and constitute the most commonly deployed method. Another advantage of the conversion module is reduced jumper complexity. Notice that a G jumper, which has a Type-B polarity and is pinless, is used to directly connect two parallel optics transceivers. That same jumper is used on both ends of the interconnect link, thus eliminating concerns about correct pinning.
In Figure 15b, the same trunk is used, but the jumper type is now labeled F. In the bill-of-materials (BoM) shown in Table 8, you can see that an F jumper still has a Type-B polarity, but on one end the MTP is pinned and on the other end a pinless MTP is used. Thus, when you install the jumper, you would install the pinned end in the patch panel, and you would install the pinless end in the electronics. However, because of the pinning, this same jumper could not be used to make a direct connection between two ports. Hence, you can see the advantages of the conversion modules, which both use all the fiber and allow a single-jumper solution.
The combined solution shown in Figure 15c might be deployed when cabling between a spine switch, where the module is placed, and a ToR leaf switch, where the conversion harness and panel are located. The QSFP ports on the leaf switch are closely clustered, so the short breakouts of the 2x3 harness assembly should not be a concern. However, use of the 2x3 harness assembly at the core spine switch is not desirable because patching across blades and chassis is a common practice.
Figure 15. 40 Gigabit Ethernet Parallel Optics Interconnect Link with (a) Conversion Modules, (b) No Conversion, and (c) Combined Conversion Module and Harness Solution
Table 8. Sample Part Numbers for Parallel Optics Cabling Options
As the demand for bandwidth, new transmission media must be developed to meet the requirements of users. The latest in optical transmission media is called OM5 fiber. To help you use this advanced fiber to its greatest advantage, this paper describes the basis of OM5 fiber, and highlights the key differences with OM4 fiber.
What Is OM5 Fiber?
According to the ISO/IEC 11801, OM5 fiber specifies a wider range of wavelengths between 850nm and 953nm. It was created to support short wavelength division multiplexing (SWDM), which is one of the many new technologies being developed for transmitting 40Gb/s and 100Gb/s. In June 2016, ANSI/TIA-492AAAE, the new wideband multimode fiber standard, was approved for publication. And in October of 2016, OM5 fiber was announced as the official designation for cabling containing WBMMF (Wide Band Multimode Fiber) by ISO/IEC 11801. From then on, OM5 may be a potential new option for data centers that require greater link distances and higher speeds.
What Is OM4 Fiber?
OM4 is laser-optimized 50um fiber having 4.7GHz*km EMB bandwidth designed for 10 Gb/s, 40 Gb/s, and 100 Gb/s transmission. OM4 fiber has been on the market since 2005, sold as premium OM3 or OM3 fiber. The OM4 cable designation standardizes the nomenclature across all manufacturers so that the customer has a clearer idea of the product that they are buying. OM4 fiber is completely backwards compatible with OM3 fiber and shares the same distinctive aqua jacket. OM4 was developed specifically for VSCEL laser transmission and allows 10 Gig/second link distances of up to 550 Meters (compared to 300M with OM3) and offers an Effective Modal Bandwidth (EMB) of 4700 MHz-km.
OM4 vs. OM5: What’s the Difference?
Since OM1 and OM2 fiber can not support 25Gbps and 40Gbps data transmission speeds, OM3 and OM4 were the main choices for multimode fiber to support 25G, 40G and 100G Ethernet. However, it’s becoming more costly for optical fiber cable to support next-generation Ethernet speed migration as bandwidth requirements increase. Against such a background, OM5 fiber was born to extend the benefits of multimode fiber in data centers.
The key difference between them is that EMB is specified only at 850 nm for OM4 fiber at 4700 MHz-km, while OM5 EMB values are specified at both 850 nm and 953 nm and the value at 850 nm is greater than that of OM4. Therefore, OM5 fiber offers users longer length distances and more choices in optical fiber. In addition, TIA has specified lime green as the official cable jacket color for OM5, while OM4 is aqua jacket. And OM4 is designed for 10Gb/s, 40Gb/s, and 100Gb/s transmission, but OM5 is designed for 40Gb/s, and 100Gb/s transmission which reduces the fiber counts for high speed transmissions.
What’s more, OM5 cable can support four SWDM channels, each carrying 25G of data to deliver 100G Ethernet using a single pair of multimode fibers. Besides, it is fully compatible with OM3 and OM4 fiber. OM5 is available globally for installations in multiple enterprise environments, from campuses to buildings to data centers. In a word, OM5 fiber is a better choice than OM4 on transmission distance, speed and cost.
OM5 fiber provides next-generation multimode fiber performance for today and tomorrow’s high speed applications. With its significantly higher bandwidth, it can be assured that multimode fiber will continue to provide the most cost effective solutions for short reach applications in data centers and LANs. OM5 precisely meets the demands, and it will be your preferable choice for your data centers.


Creating a robot that elicits love. How do you make people protect a robot? By eliciting love through designed human-robot interaction. Our robot's form had to be perceived as friendly, small, and approachable, all within strict engineering contraints. We transformed a looming 6-foot-tall robot into a short and friendly robot, without making it appear interactive.
I was the designer for this project done at Bossa Nova Robotics in 2015.
Bossa Nova uses a robot to collect data in big box retail stores. Through HRI research, we knew Bossa Nova’s current robot looked techy, fragile, and expensive. We needed to design a new form that presents a persona that is accepted and loved, so that shoppers allow the robot to do its job.
Through HRI research we knew there were aspects of the form of Bossa Nova’s robot that needed to change to gain acceptance from shoppers. In collaboration with industrial design and mechanical engineering, we designed a robot that shoppers will love.
The previous generation of Bossa Nova’s robot balanced on two wheels, much like a Segway. While this is a cool engineering feat, the sight makes shoppers uncomfortable—especially when the robot transitions from a balancing to non-balancing state by falling back onto casters. The robot appeared fragile, and its movements were jerky. Shoppers were uncertain about how to move around the robot because they were afraid they would knock it over. We don’t want our robot to negatively affect the shopping experience, and making customers uneasy was a negative. Fortunately, it was to the benefit of both engineering and design goals to have a statically stable robot, so we could make the next-generation robot non-balancing.
Our robot needed to appear robust and friendly. This meant moving beyond the dark colors and hard lines of the masculine stereotype seen so frequently in today’s technology. This was an opportunity to make robotics more relatable. If this robot becomes part of everyday life, the way it looks could go a long way to changing stereotypes. At the same time, the robot couldn’t look too friendly, or it would invite interaction from shoppers. We don’t want people touching it. The robot can’t have traditional humanoid features, otherwise it would appear too interactive. This all made designing communication patterns much more interesting.
Another consideration was that the robot is going to be on its own without a handler, and people would be more likely deter the robot from its goal if it elicited feelings of disgust and rage. Instead, we had to find a form that would elicit love and adoration with the right balance of cuteness; too far on the cute side of the spectrum and it could invite more interaction than we’d like.
It’s really hard to make a 6-foot-tall robot cute. To make it even more difficult, required the next version of the robot to be even taller. Somehow, we needed to shrink the robot. We had a hunch that we could do this by visually separating the parts of the robot that were required to be tall from the parts of the robot that drove it around. This way, what shoppers would describe as the “robot” appeared to be only 3 feet tall, dragging along the part that was 6 feet tall.
We worked with an industrial design firm that created a new shape to meet all of these goals. We then had a foam model of that shape made, and we attached it to a drive train. We took this mobile foam model into retail stores, drove it around, and asked shoppers what they thought. To our delight, the visual separation of the shapes worked. When shoppers talked about the robot, they looked down at the small 3-foot form instead of up at the top. Shoppers thought of the robot as small, despite the fact that it was over 6 feet tall.
People also had behaviors towards the robot that suggested they found it cute. One store employee even patted the top of the small form while saying, “Hey, buddy,” with an endearing tone. Kids also loved it. They ran up and gave it bear hugs, and they stood in front of it trying to play.
Through these interactions we realized that we may want to increase the height of the form perceived by shoppers as the actual robot. Despite how cute the interactions with the kids are, we want to avoid having the robot sit at at exactly kid height because it could interfere with the robot’s data collection. Testing also revealed some other negative connotations, so we are still working with another industrial design firm to iterate on the shape. This is an ongoing project, and the new form will be released mid-2017. Once we have a shape, we will be integrating communication patterns and new behaviors.


3.3 Auxiliary function of Airtest script recording¶
Airtest is a non-intrusive test framework based on image recognition.
The Airtest test framework provides a large number of test API, and we can use these methods flexibly in test scripts to implement test functions.
Common API in Airtest include three types:
device operation and
assertion.The Airtest Recording Assistant window is provided in AirtestIDE to quickly generate Airtest common statements. This chapter focuses on how to quickly generate Airtest scripts using AirtestIDE.
1. Recording auxiliary window of Airtest script¶
There are three types of recording buttons in the Airtest Recording Assistant window of AirtestIDE:
|Operation type||Auxiliary type||Assertion type|
2. Auxiliary button for recording a script¶
After clicking the
touch/swipe/wait/exists/assert_exists/assert_not_exists button, please press the left mouse button on the device screen to select the screenshot box, and raise the left mouse button to complete the frame selection. The corresponding operational statement is automatically inserted into the script of the editor.
It is worth noting that if it is the Windows embed mode, after you pop up the left mouse button, you need to double-click to complete the box selection.
3. Script automatic recording function¶
After clicking the Auto Record button, you use the mouse to operate the device screen, and the corresponding operational statement is automatically inserted into the script of the editor.
4. Insert screenshot function¶
Click the "Insert Screenshot" button, then select the screenshot on the device screen, and the corresponding image will be automatically inserted into the editor's script.
You can use this function to customize the logical encapsulation of images, such as recognizing a few images in a loop.


NEMA Twist Lock Plug Chart: Identify Your Plug
You are welcome to our comprehensive guide on NEMA twist lock plugs! If you’ve ever struggled to distinguish the proper plug to your electrical equipment, this is actually the resource for you personally. Our NEMA Twist Lock Plug Chart provides everything you have to pick the correct plug according to amperage, voltage, and configuration.
With standardized codes and organized charts, it is simple to get the perfect plug for your specific needs. Say goodbye to compatibility issues and confusion – our nema l6-20r wiring diagram can make it easy to identify and select the right plug for the setup.
So, if you’re ready to accept guesswork out of discovering the right plug, let’s dive to the world of NEMA twist lock plugs and see how our chart can simplify your life.
Understanding NEMA Twist Lock Plug Standards
This section provides an introduction to the NEMA twist lock plug standards. The objective of these standards is always to ensure compatibility, safety, and reliability in electrical connections. The NEMA standards define the configuration, voltage, amperage, as well as other specifications for a number of twist lock plugs.
These standards are necessary for selecting the best plug for specific applications and ensuring proper and safe electrical connections. By implementing the NEMA twist lock plug standards, users might have confidence in the performance and longevity of their electrical equipment.
The Entire NEMA Twist Lock Plug Chart
In this section, we present the total NEMA Twist Lock Plug Chart, which serves as a comprehensive reference for anyone utilizing twist lock plugs. The chart provides more information about the amperage, voltage, and configuration of every plug, making it easier to determine the right plug for specific electrical needs. Arranged inside a tabular format, the chart provides a user-friendly display of your essential specifications, ensuring quick and accurate plug selection.
The NEMA Twist Lock Plug Chart includes:
- Amperage: The actual capacity for each plug, measured in amperes (A).
- Voltage: The electrical potential difference maintained by each plug, measured in volts (V).
- Configuration Details: Information on the number of prongs and grounding requirements for every single plug.
This comprehensive chart is an invaluable tool for electricians, technicians, and DIY enthusiasts, providing them with the necessary information to create informed decisions when picking the right twist lock plug for specific applications. Whether you’re seeking a plug with a certain amperage, a certain voltage rating, or even a particular configuration, the NEMA Twist Lock Plug Chart has you covered.
Deciphering NEMA Locking Plug Configuration Chart
In order to know the specific characteristics of each and every NEMA locking plug, it is very important decipher the NEMA locking plug configuration chart. This chart utilizes a coding system that offers valuable specifics of the configuration of every plug. By understanding these codes, users can navigate the chart effectively and choose the correct plug for his or her needs.
The NEMA locking plug configuration codes comprise of a mix of numbers and letters. Each code represents a specific configuration, providing details about the number of poles, grounding requirements, and other important characteristics. By discovering how to interpret these codes, users can rapidly identify the plug that is best suited for their electrical setup.
Let’s look into some common instances of NEMA locking plug configuration codes:
|Locking plug with 2 poles and a grounding requirement
|Locking plug with 3 poles, a grounding requirement, plus a twist lock design
|Locking plug with 2 poles, a grounding requirement, along with a straight blade design
By referring to the NEMA locking plug configuration chart and understanding the meanings of such codes, users can confidently pick the appropriate plug for his or her specific applications. This helps ensure proper compatibility and safe electrical connections.
Seeing that we certainly have deciphered the NEMA locking plug configuration chart, we can easily start working on exploring the detailed wiring diagrams for specific NEMA plug types.
A Comprehensive Look into NEMA L6 20R Wiring Diagrams
In this section, we will provide a detailed exploration of NEMA L6 20R wiring diagrams. Knowing the connections and wiring guidelines with this specific twist lock receptacle is essential for ensuring safe and reliable electrical connections.
To properly wire and connect NEMA L6 20R receptacles, it is important to comprehend the different terminals and wires involved. Below, we present a step-by-step guide that will facilitate your understanding and allow you to confidently wire NEMA L6 20R receptacles.
- Start with identifying the four terminals about the NEMA L6 20R receptacle. These terminals are labeled using the following designations:
- Hot (X)
- Hot (Y)
- Neutral (W)
- Ground (G)
Following these wiring guidelines and connecting the NEMA L6 20R receptacle correctly provides you with a safe and secure and reliable electrical connection. It is very important to comply with these guidelines and consult the right wiring diagrams to your specific electrical setup.
Advantages of Using Twist Lock Receptacle Chart
With regards to electrical connections, using a twist lock receptacle chart offers numerous advantages. By making reference to this chart, you can simplify the procedure of identifying and choosing the right twist lock receptacle for your specific needs. Let’s explore a number of the key advantages of choosing a twist lock receptacle chart:
- Compatibility: The twist lock receptacle chart ensures compatibility involving the receptacle along with your electrical equipment. The chart provides details regarding the amperage, voltage, and configuration for each receptacle, allowing you to select the one which matches your preferences.
- Safety: Using the correct twist lock receptacle is vital for maintaining electrical safety. The receptacle chart allows you to find the appropriate receptacle that suits the necessary safety standards and ensures reliable connections.
- Time-saving: As an alternative to putting things off searching through various options and specifications, a twist lock receptacle chart streamlines the procedure. It gives each of the information you need in one place, letting you quickly choose the right receptacle for the electrical connections.
- Mistake prevention: Creating a mistake when deciding on the wrong receptacle can lead to equipment damage or electrical hazards. The chart minimizes the risk of errors by offering clear details and guidelines, assisting you make informed decisions.
- Optimal connections: Using a twist lock receptacle chart, it is possible to ensure optimal electrical connections. The chart can help you pick the receptacle using the correct amperage, voltage, and configuration, ensuring efficient power delivery and reducing the possibilities of electrical issues.
By leveraging the main advantages of using a twist lock receptacle chart, you are able to streamline the entire process of selecting the most appropriate receptacle, ensure safety and compatibility, and achieve optimal electrical connections.
Incorporating Twist Lock Plug Types along with their Uses
With this section, we will explore the many twist lock plug types and their specific applications. Learning the various twist lock plug options available for sale, for example NEMA L5-20, L14-30, and L6-20, is important for selecting the most appropriate plug for the electrical needs.
Let’s take a close look at each twist lock plug type along with their recommended uses:
- NEMA L5-20: This twist lock plug type is typically found in industrial settings when a reliable and secure electrical connection is needed. It is often located in equipment like servers, generators, and motor controllers. The NEMA L5-20 plug includes a current rating of 20 amps along with a voltage rating of 125 volts.
- NEMA L14-30: The NEMA L14-30 twist lock plug would work for applications which involve high power consumption. It can be popular in commercial and residential environments where heavy machinery, for example air compressors and welding machines, is used. This twist lock plug has a current rating of 30 amps plus a voltage rating of 125/250 volts.
- NEMA L6-20: The NEMA L6-20 twist lock plug is often employed in environments where safety factors paramount. It really is commonly located in hospitals, laboratories, and data centers where reliable power distribution is necessary. This plug type carries a current rating of 20 amps along with a voltage rating of 250 volts.
By comprehending the specific applications of each and every twist lock plug type, you may choose the appropriate plug to your electrical setup. Regardless if you are doing work in a commercial facility, a residential property, or possibly a commercial building, selecting the right twist lock plug is vital for ensuring a safe and secure and efficient electrical connection.
|Twist Lock Plug Type
|Current Rating (Amps)
|Voltage Rating (Volts)
|Servers, generators, motor controllers
|Air compressors, welding machines
|Hospitals, laboratories, data centers
Integrating 20A 250V Twist Lock Receptacles inside your Setup
Integrating 20A 250V twist lock receptacles inside your electrical setup requires consideration and adherence to proper installation guidelines. Following the tips and guidelines outlined below, you are able to ensure a easy integration that guarantees proper electrical connections and optimal safety.
- Wiring: Before integrating 20A 250V twist lock receptacles, be sure that the wiring within your setup is capable of doing handling the voltage and amperage requirements. Use appropriate gauge wires and follow the recommended wiring guidelines for your specific electrical setup.
- Grounding: Proper grounding is vital for your safe operation of twist lock receptacles. Make sure that your setup features a reliable grounding system that conforms to electrical codes and regulations. Consult a certified electrician in case you have any doubts or concerns.
- Compliance: It is very important to conform to all relevant electrical codes and regulations when integrating 20A 250V twist lock receptacles. Fully familiarize yourself with local building codes and talk to a certified electrician to guarantee compliance with all necessary requirements.
- Safety Precautions: Always prioritize safety when working with electrical setups. Use appropriate personal protective equipment (PPE) and follow standard safety practices. When you are unsure about any aspect of the installation process, seek the help of an experienced professional.
- Testing and Verification: After integrating 20A 250V twist lock receptacles, perform thorough testing and verification to make certain proper functionality and electrical connections. Use appropriate testing equipment to ensure that the receptacles are operating as intended.
By following the following tips and guidelines for integrating 20A 250V twist lock receptacles, it is possible to confidently incorporate them to your electrical setup, ensuring reliable and safe electrical connections. Always prioritize safety and talk to professionals if needed.
|Methods for Integrating 20A 250V Twist Lock Receptacles
|Ensure proper wiring able to handle the voltage and amperage requirements
|Implement a trusted grounding system that conforms to electrical codes
|Abide by all relevant electrical codes and regulations
|Prioritize safety by making use of appropriate PPE and following safety practices
|Perform thorough testing and verification after installation
Wrapping It Up
In conclusion, the NEMA Twist Lock Plug Chart is definitely an invaluable resource for everyone working with twist lock plugs. It provides a comprehensive overview of the various plug types, their amperage, voltage, and configuration details. By making reference to this chart, users can certainly identify and select the best plug for their specific electrical applications.
Utilizing the NEMA twist lock plug chart allows for precise compatibility, ensuring safe and reliable electrical connections. Adhering to the NEMA standards outlined in the chart is essential to protect yourself from any potential issues and also to keep the overall safety and efficiency of electrical setups.
We encourage readers to consult the NEMA twist lock plug chart when working with twist lock plugs and receptacles. By using the knowledge gained from this article and using the chart, readers can make informed decisions, avoid costly mistakes, and get optimal electrical setups. If you are a professional electrician or a DIY enthusiast, the NEMA twist lock plug chart is your essential help guide to selecting the most appropriate plug for the electrical needs.


IKEA’s latest product launch is more tech than product. They’ve introduced a series of LED bulbs and dimming accessories (Tradfri) that make light control kind of a cool thing. Watch this video and be amazed by the magic of this little round disk…
I mean, it’s seriously the best thing from IKEA since they introduced the much-loved Billy Bookcase!
Ok. Maybe Billy is still the best.
I love that it can change the colour of the bulbs too from warm yellow to cool bluish tones. You know where I’ll be this weekend!


Intellitec Battery Isolator Relay Delay 00-00629-120
Delays The Function Of The Isolator Relay When The Coach Is Started
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Intellitec Battery Isolator Relay Delay
Intellitec’s Battery Isolator Relay Delay/E offers a low cost, reliable approach to charging multiple batteries. Unlike diode isolators, this system provides an engine driven alternator with the opportunity to begin charging the main battery before connecting the auxiliary battery. This allows the use of self-exciting alternators and lets the engine briefly warm up prior to placing the load of a heavily discharged auxiliary battery on the alternator. The unit is available in both 12 and 24 Volt versions. The unit is fully encapsulated in a plastic enclosure for mounting in the engine compartment with two screws. It operates in combination with a conventional continuous duty cycle isolator relay that has been used by a number of vehicle manufacturers. There are three (3) wires to connect to the delay unit: one from an ignition switched 12 Volt source, a ground and the isolator relay coil. It operates by sensing the voltage on the main 12 Volt system. When this voltage goes above 13.3 Volts for approximately 12 seconds, as happens when the engine is running normally (normal alternator output voltage is approximately 14.4 Volts), it will close the isolator relay providing charging current to the auxiliary battery. When the ignition switch is turned off, the relay will open immediately.
Used For: Delays The Function Of The Isolator Relay When The Coach Is Started
Voltage Rating: 12 Volts
- Bi-Directional Isolator Relay Delay Offers A New Approach To Charging Batteries In An RV Application
- Provides An Engine Driven Alternator With The Opportunity To Begin Charging The Main Battery Before Connecting The Auxiliary Battery
- Allows The Use Of Self-Exciting Alternators And Lets The Engine Briefly Warm Up Prior To Placing The Load Of A Heavily Discharged Auxiliary Battery On The Alternator
- Fully Encapsulated In A Plastic Enclosure For Mounting In The Engine Compartment With Two Screws
- Operates In Combination With A Conventional Continuous Duty Cycle Isolator Relay That Has Been Used By A Number Of Vehicle Manufacturers
- Limited 90 Day Warranty
|Specifications of Intellitec Battery Isolator Relay Delay 00-00629-120|
|Used For||Delays The Function Of The Isolator Relay When The Coach Is Started|
|Voltage Rating||12 Volts|
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IoT stands for “Internet of Things,” and refers to the concept of connecting everyday objects to the internet and other devices to enable them to exchange data and perform useful functions. This can include everything from home appliances and wearables to cars, industrial equipment, and entire cities.
Some of the latest inventions in IoT are:
- Smart homes use IoT: technology to automate and control various devices and systems within a home, such as lighting, security, and temperature. Smart home devices can be controlled remotely via a mobile app or voice assistant and can learn from users’ behavior to adjust settings automatically.
- Wearables – Wearable IoT devices, such as smartwatches and fitness trackers, are becoming increasingly popular. These devices can track fitness metrics, monitor health conditions, and even provide real-time feedback during workouts.
- Smart Cities – IoT technology is being used to improve urban infrastructure and services, such as traffic management, waste management, and public safety. Smart city solutions can help reduce congestion, improve air quality, and enhance overall quality of life for residents.
- Industrial IoT – IoT technology is also being used to optimize and automate industrial processes, such as manufacturing and supply chain management. By connecting machines, sensors, and other devices to a central system, businesses can monitor and control their operations more efficiently and effectively.
- Autonomous Vehicles – Autonomous vehicles, such as self-driving cars, use IoT technology to sense their environment and make decisions based on data from cameras, radar, and other sensors. These vehicles have the potential to reduce traffic accidents, improve traffic flow, and provide greater mobility for people who are unable to drive.
The potential applications of IoT technology are vast, and it is likely that we will continue to see significant advancements in the coming years.


8/30/2010 - 12/22/2010
12:00 PM - 12:00 PM
Direct current (DC) theory and the fundamentals of series and parallel DC circuits. An introduction to the concept of electricity and its behavior with respect to conductors and resistance devices. The study of alternating current (AC) circuits begins with the generation of a sine wave and review of trigonometric functions and continues through resonance and filter circuits. In-depth look at inductors and capacitors and how they effect and AC and DC circuit differently.
||Check your grades using Gradebook. Be sure to bookmark this page for fast access.


Highland Park Electric
Commercial Electrician in Highland Park, Texas
24 HOUR EMERGENCY SERVICE AVAILABLE!
Commercial Transformer Basics
Once wiring is pulled in the ground from the building all the way around the transformer and the pads are down, we go from the high transformer to the low, which is the step-down.
We pull in our high voltage, our low voltage, our ground, we’ve done the 2 high voltage lugs and then we’re ready to ground it. We scrape around where we’re going to land our grounds by scraping the paint off and trying to get down to the metal before grounding it.
Transformers are capable of receiving AC power at one voltage and delivering that power at another voltage. The purpose of transformers is to help achieve better transmission efficiency while transferring the power over longer distances.
In thinking about how a three phase transformer, we can start by looking at it in the most simple terms. At the core, a transformer is simply electromagnetic induction. According to this principle of varying magnetic flux associated with a loop will induce an electromotive force across it.
A fluctuating magnetic field like this can easily be produced by a coil and an alternating EMF system. A current carrying conductor produces a magnetic field around it, while the magnetic field produced by a coil will fluctuate around the coil. Because of the fluctuating nature of the alternating current, the magnetic field associated with the coil will also fluctuate accordingly.
It’s possible to effectively link this magnetic flux to a second winding through a core made up of ferromagnetic material. This fluctuating magnetic field will cause an EMF in the secondary coils due to the electromagnetic induction present. Because the turns are arranged in a series of turns, the sum EMF induced across the winding will include the total of the individual EMFs induced in each individual turn.
Because the same magnetic flux is passing through both the primary coil and the secondary coil, the EMF per turn for both the primary and secondary coils will be the same. The applied input voltage dictates the EMF per turn for the primary coil. As a result, the induced EMF at the secondary coil is expressed as follows.
What this means is that it’s possible to lower the voltage with fewer turns in the secondary than in primary. For the reverse case, you can increase the voltage. Since that energy is conserved, the primary and secondary currents must obey the required relationship. The way three phase transformers work is they use three such single phase transformers, albeit with a slightly different coil configuration.
In that case, the primary and secondary coils sit concentrically. A three phase transformer requires two more of these windings. Transformers that have high power ratings generally use a special winding often referred to as a disk type winding. Separate disk windings are usually connected in series through outer and inner crossovers.
Coils and Windings
The low voltage windings are connected together in a delta configuration and the high voltage windings are connected together in a star configuration. Thus, the line voltage further rises to route three times at high voltage side. What this means is that from a three phase step up transformer, it is possible to draw four output wires. The four wires include three phase power wires and one neutral. High Voltage insulated bushings are required to bring out the electrical energy.
The core of the three phase transformer is made of a thin, insulated steel lamination. Such steel laminations are stacked together as shown to form the three phase limbs. The primary purpose of thin laminations is to reduce the total energy loss due to the eddy current formation.
The low voltage windings usually sit near the core and various kinds of energy loss happens while transferring power from the primary to secondary coil. All these energy losses are dissipated as heat. Transformers like these are usually immersed in a cooling oil to dissipate the heat and keep the temperature low. The oil dissipates the heat via natural convection. Oil in the tank will expand as it absorbs the heat, so a conservator tank helps to accommodate for this volume change.
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Gas Igniter Manufacturer
As the name implies, gas ignitors (or Spark Generator) light the gas for heating purposes by generating heat instantaneously. When people turn on the switch of a gas stove, oven, pizza oven, or boiler, the igniter generates a high voltage and heats up to a specific temperature to light the gas. They are generally divided into the following categories,
- Piezo Igniter
- AC/DC Pulse Igniter
- Hot Surface Igniter
What is the Gas Igniter System?
Unlike others, I’m used to dividing gas ignition systems into two types— pilot ignition systems and spark ignition systems. If you can’t remember them quickly, you can understand them more straightforwardly as “the system with actual flame ignition” and “the system without actual flame ignition”.
Subdivided downwards you can divide them into.
- Pilot ignition
- Piezo ignition
- DC or AC pulse ignition
- Hot surface ignition
You can also divide them into manual and automatic ignition.
Piezo igniter is also called gas lighter or spark igniter. It belongs to the manual ignition system generally used on gas stoves. It uses a physical phenomenon called the piezoelectric effect to produce an electric spark by hitting a crystal to ignite the gas in the burner.
The other three you can think of as automatic ignition systems, also called electronic ignition systems. Only the pilot ignition will produce a real flame, and the others only have a spark to ignite. Note that DC pulse ignitors require installing a dry cell battery, meaning you need to change the dry cell battery often. On the other hand, AC pulse and hot-surface ignitors need to be connected to a power source to work.
Automatic ignition systems are safer and more stable than manual ignition systems, but they require power to maintain them regularly. There’s no denying that you’ll hardly ever see manual ignition systems in high-end kitchen appliances.
Product By Bngas Models
Product By Varieties
DC Pulse Igniter
DC Pulse Igniter generates a continuous instantaneous electric spark to ignite a gas-fired electronic product. Application range: gas stoves, stoves, water heaters, gas lamps, barbecues, and other gas appliances.
Spark output terminal: 1~6 output terminals
Input power: One AA battery (1.5V )
Output voltage: ≥22KV
AC Pulse Igniter
Electrical igniters have screw fixation, clip fixation, and self-switched bodies.
Models from 1 to 8 outlets in different housings suitable for gas hobs, free-standing cookers, and hollers applications, available with or without a switch and EMC filter.
SUPPLY VOLTAGE: AC 110~220V, AC 220~240V, AC 120V, OR DC 1.5 V, DC 3 V
SUPPLY FREQUENCY: 50-60 Hz
POWER: 0.6 VA-1.1 VA
SPARKING VOLTAGE:> 10 kV @30pF
SPARK GAP: 3-5 mm
Piezo ignitor, also called the “push button” igniter. It’s used in gas grills, portable camping stoves, and other devices.
The Piezo ignitor consists of a small spring-loaded hammer and a piezoelectric crystal. When the button on a piezoelectric ignitor is pressed, the spring-loaded hammer strikes the crystal, which creates a voltage when deformed. This sudden forceful deformation produces a high voltage and subsequent electrical discharge. The ignitor then sends this high-voltage electrical charge along the wire to the electrode, which ignites the gas.
Hot Surface Igniter
These igniters are composed of advanced ceramic materials. These devices are also the most commonly used electronic ignition systems today. They are generally employed for applications such as space furnaces and heaters. Hot surface igniters are widely used for their reliability and durability potential.
Silicon nitride (WHICH BNGAS HAVE) is a chemical compound of silicon and nitrogen. It is a hard ceramic with high strength and is durable over a broad temperature range. Its notable characteristics include durability over a high-temperature range.
The piezoelectric igniter uses nylon plastic material with a maximum temperature resistance of 120°C and an output voltage of 13.6kV or more. The recommendable arcing distance is 3.5-4.0 mm.
The average life span is over 30,000 cycles. Installation methods are snap type and screw plug type. They are commonly used in kitchen appliances.
DC Pulse Igniter
This DC spark generator is commonly available with spurious or genuine keys (as shown below). The output voltage is generally ≥ 22kV and is powered by a single AA/AAA battery or an external battery pack.
But generally, a good user experience is not to hold the ignition keys. Just turn the knob to ignite the fire.
AC Pulse Igniter
Electronic igniters are pulse igniters made of PA66, which are more common in kitchen appliances. Various operating voltages are available, and the switches and EMC can be selected. The Spark gap of 3-5mm can work properly.
SPARKING VOLTAGE:> 10 KV @30pF
Hot Surface Igniter
Silicon nitride ceramic igniter is the latest and most advanced hot surface ignition technology application. It completely avoids the disadvantages of silicon carbide heating element, which is sparse, brittle, and afraid of water.
Silicon nitride has a high working temperature, fast heating up speed is dense and strong, and has a long working life.
Silicon nitride has the following advantages: high working temperature, fast heating up speed, dense and solid, long working life, etc.
Why Choose BNGAS Customize Gas Igniters?
Our automated machinery can guarantee the stability and safety of the spark generator to encapsulate the epoxy. In strict accordance with ISO9001, CE, and CSA production standards, we provide customers with perfect products so that the electrical equipment can operate more stable.
The finished product needs to be tested 100% pressure resistance test and appearance inspection. We will conduct continuous voltage resistance tests for at least 5 hours to test the voltage resistance of the products. We will perform the freezing test at -33 degrees Celsius for at least three days for individual products with low-temperature requirements.
Gas Igniter Ultimate FAQ Guide
The gas igniter is an essential component of a gas oven with which to heat it. It works by igniting the gas in the pipe with an electric spark and creating a flame to heat it. Therefore, this crucial part is needed every time it is ignited, so it needs to be maintained or replaced regularly.
It is easy to buy the wrong gas ignition wire. Many burners use ignition electrodes similar to spark plugs or tail terminals alike, and people mistakenly think that car spark plug wires can also be used on burners. But this does not fit.
Because EPDM rubber cannot withstand high temperatures, automotive spark plug wires use an EPDM rubber (ethylene propylene diene monomer) casing with a maximum temperature of only 266°F (130°C). Gas ignition wire for combustion applications uses high-temperature silicone wires that can reach a maximum temperature of 482°F (250°C). This temperature rating determines the working life of your gas ignition wire.
The gas ignition wire must be adapted to the electrode tails, or there will be a safety hazard.
Standard terminals for combustion applications are shown below. These will fit most ignition electrode tails, and some less common ones can be customized.
It depends on the style, model, and order quantity. The price range is $0.60-$30.00
According to your order quantity, it is estimated to take 15-40 working days.
Yes, we have the CE, CSA, IMQ, ISO9001, etc.


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The programme provides mastery over advanced topics in Embedded Systems, Wireless Broadband Communications and Digital Signal Processing to enable students straddle the overlapping fields of Electronics, Communications and Computer Science.
- 4 Years
- 12TH PCM- 50% GEN, OBC & 45% SC/ST
- Affiliated to Dr. APJ Abdul Kalam Technical University, Lucknow, UP.
Job Opportunities you can choose after the course
- Service Engineer
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The internet of things is making its way into many industries and plenty of connected devices are evolving. In that manner, the real estate is never left behind, as it sees the Salesforce automation boom in recent years. Salesforce automation in real estate deals with infrastructure along with technology where devices such as electrical outlets, thermostats, plumbing, lighting system, etc. are connected through the internet and work as smart systems.
A good example of Salesforce automation in real estate would be smart lighting where lighting possesses few conditions. The lights turn on and off when individuals are present in or out of the home, also dim and bright factors are set depending on the presence of natural light. In the same manner, a Wi-Fi enabled water heater is yet another device that optimizes water temperature and provides water in need. With these features, homeowners find it easier, energy-efficient, and find a reduction in energy costs.
Salesforce automation in real estate:
The sales force management solutions in real estate help the user to plan, manage, and get real-time insights into their field sales and marketing activities. From tracking the attendance of the sales executives and their location, helps in taking orders, manage collections capture stock, and also track visibility. There are several advantages in using SFA in real estate, and those are summarized as follows,
Any inquiries made by customers wait for an immediate reply which is tough for agents. In that case, chatbots for real estate are perfect as they give an immediate reply. This leads to strengthening customer relationships with the firm and also retaining them. The designs of the automation tools are according to the requirements of the user. The user-specific feature is a unique aspect of a chatbot. By understanding the need of the customer, they offer solutions.
It helps in efficient follow up of all clients and skate holders, following every client on a regular time base is difficult. In that manner chatbot for real estate are perfect followers. Either through a text or email message, they follow clients regularly. In this way, the possibility of retaining the customer is more and the client gains an idea of approaching.
The use of salesforce automation in real estate is also by beacon technology. Beacons are Bluetooth devices in an arena. They send all mandatory details such as photos, price, square footage, 360 virtual tours, etc. to the buyer’s phone. For example, with Beacon, Sage clients possess the capacity to view the site before the agent reaches. As the client runs into the beacon’s radius, there is the identification of a beacon signal and link sent to start viewing the property.
The sales force automation service provider’s servers in cost and time effective management. The analytical tool of SFA acts smarter and quicker in crunching the data and act at a faster pace. The use of history orders supports the company in taking crucial decision-making processes and in proposing predictions too.


لوحة تحكم مولدات الكهرباء موديل 5110
The Model 5110 is an Automatic Engine Control Module. The module is used to automatically start and stop the engine,indicating the operational status and fault conditions by means of an LCD display and a flashing LED on the front panel.
Selected operational sequences, timers and alarms can be altered by the user.
Alterations to the system are made using the 55xx configuration software with the 810 interface and a PC. This interface also provides real time diagnostic facilities.
It is also possible to monitor the operation of the system either locally or remotely.
Access to the module is protected by PIN number to prevent unauthorised access.
Micro-processor based design PC or front panel configuration
Automatic engine starting and stopping
Automatic shutdown on fault condition
Custom graphical icon type display
Provides engine and generator instrumentation
Provides engine alarms and status information
Front panel configurable inputs,outputs, alarms and timers.
LED & LCD alarm indication Compatible with 5200 series modules for easy upgrade path.
The 5110 module provides engine and electrical metering facilities via the LCD display with the following instrumentation displays, accessed via the SCROLL push-button:
*Generator Volts L1-N, L2-N, L3-N
*Generator Volts L1-L2, L2-L3, L3-L1
*Generator Amps L1,L2, L3
*Generator Frequency Hz
*Engine Speed RPM
*Engine Oil Pressure (PSI & Bar)
*Engine Temperature (oC & oF)
*Plant Battery Volts
*Engine Hours Run


I am an Assistant Professor and Canada CIFAR AI Chair in the School of Computer Science at McGill University and at Mila – Quebec AI Institute. My group’s work focuses on innovations in machine learning driven by problems in climate change – encompassing areas such as biodiversity monitoring, land use classification, climate model emulation, and materials discovery. We also work on mathematical understanding of the properties of neural networks.
I also serve as Co-founder and Chair of the global nonprofit Climate Change AI, Scientific Co-director of Sustainability in the Digital Age, and Canada lead for the US-Canada NSF Global Center on AI and Biodiversity Change (ABC). In 2021, I was named to the MIT Technology Review “35 Innovators Under 35” list for work in building the field of machine learning and climate change. Previously, I was an NSF Mathematical Sciences Postdoctoral Research Fellow at UPenn and an NSF Graduate Research Fellow at MIT.