1. Field of the Invention
The present invention relates to a multi-function and easy-to-use cordless telephone set.
2. Description of the Prior Arts
The applicant of the present invention has proposed in Japanese Patent Application No. HEI 6-214612 a cordless telephone set which can be connected with a variety of digital switching equipment of different protocols. The proposal was made to improve the current situation where cordless telephone sets are not commonly used in business offices because the protocols employed by digital PBXs which are used widely now differ from manufacturer to manufacturer.
FIG. 1 is a block diagram indicating constitutions of a main unit X of a cordless telephone set CT as proposed in the above patent application and a subunit Y coupled by wireless with the main unit. The main unit X of the cordless telephone set CT transmits control data and voice data on a time division basis or through a duplex bidirectional transmission system between a digital PBX through a PBX line. The constitution and operations of the main unit X will be explained hereafter for every transmitting direction with reference to FIG. 1.
When data is transmitted to the cordless telephone set CT from the digital PBX, a data transmitting/receiving circuit 2 of the main unit X receives audio data and control data specified by the protocol of the digital PBX, those data being transmitted from the digital PBX through the PBX line, and separately extracts the audio data and control data under the control of a timing signal to respectively send the control data to a protocol conversion circuit 4 and the audio data to a transmitter 10. Since the PBX line employs a system in which two wires are commonly used for transmission and reception of data or a system in which two sets of two wires are provided for transmission and reception, respectively, depending on the protocol of the digital PBX, the data receiving/transmitting circuit 2 must be structured in such a manner as to correspond to the number of interface lines of the PBX line.
The protocol conversion circuit 4 is used for conversion between control data specified by the protocol of the digital PBX connected and inherent control data (hereinafter referred to as "inherent control data") of the cordless telephone set CT. For performing such conversion, a ROM 6 which stores a look-up table indicating the correspondence between the control data specified by the protocol of the digital PBX and the inherent control data is built in the protocol conversion circuit 4. Therefore, the protocol conversion circuit 4 and ROM 6 corresponding to the protocol must be used if the protocol of the digital PBX to which the cordless telephone set CT is to be connected is different from the protocol of the PBX currently connected. A control circuit 8 has a control function which is required for an ordinary cordless telephone set. That is, the control circuit 8 receives inherent control data from the protocol conversion circuit 4, determines the content of the control, activates a transmitter 10 depending on the received inherent control data, and transmits from the transmitter 10 the control data and audio data corresponding to the inherent control data to the subunit Y of the cordless telephone set CT through a transmission/reception switching circuit and an antenna 12. The control circuit 8, transmitter 10, antenna 12 and transmission/reception switching circuit and receiver 14 are common to the cordless telephone set of the prior art.
For the purpose of connecting the PBX line to a digital telephone set TL, a data distribution/combination circuit 40 is provided in the side of the input to the data transmission/reception circuit 2 to distribute control data and audio data specified by the protocol of the digital PBX from the PBX line to the main unit X and digital telephone set TL and to transmit control data and audio data transmitted from the main unit X or digital telephone set TL to the PBX line. Between the PBX line and the data distribution/combination circuit 40, a first relay 42 is provided to switchingly connect the PBX line to the main unit X or the digital telephone set TL. If the PBX line employs the system where two wires are used in common for transmission and reception, a pair of movable contacts 42-1 of the first relay 42 are connected to the PBX line, while a first pair of stationary contacts 42-21 of the relay 42 are connected to the data distribution/combination circuit 40.
A second pair of stationary contacts 42-22 of the relay 42 and the data distribution/combination circuit 40 are connected to the digital telephone set TL through the second relay 44. Specifically, a pair of movable contacts 44-1 of the second relay 44 are connected to the digital telephone set TL, while a first pair of stationary contacts 44-21 of the second relay 44 are connected to the data distribution/combination circuit 40 and a second pair of stationary contacts 44-22 of the second relay 44 are connected to the second pair of stationary contacts 42-22 of the first relay 42, respectively.
A voltage monitoring circuit 46 is also provided in the main unit X to monitor whether a regular voltage is supplied from a power source (not shown) or not. When the regular voltage is supplied, the monitoring circuit 46 gives a signal of logical "1" to one input of an AND circuit 48. Since the protocol conversion circuit 4 usually gives a signal of logical "1" to the other input of the AND circuit 48, as shown in the figure, the AND circuit 48 applies the signal of logical "1" to the first relay 42 and the second relay 44, whereby, in the first relay 42, the movable contacts 42-1 are connected to the first pair of the stationary contacts 42-21, while, in the second relay 44, the movable contacts 44-1 are connected to the first pair of the stationary contact 44-21. However, when the voltage supplied to the main unit X becomes lower than the regular voltage, the voltage monitoring circuit 46 gives a signal of logical "0" to the AND circuit 48 to set the output of the AND circuit 48 to be in the state of logical "0", whereby the movable contacts 42-1 of the first relay 42 and the movable contacts 44-1 of the second relay 44 are respectively connected to the second pairs of the stationary contacts 42-22, 44-22, and the PBX line is forced to be connected to the digital telephone set TL.
The control circuit 8 is provided with two switches SW-1, SW-2. The switch SW-1 is turned ON to transfer communication to the digital telephone set TL when a user is talking over the cordless telephone set CT. When the switch SW-1 is closed, the control circuit 8 determines that a command to transfer communication to the digital telephone set TL from the cordless telephone set CT is issued and sends corresponding control data to the conversion circuit 4. Upon reception of this control data, the conversion circuit 4 transmits a signal of logical "0" to the AND circuit 48 to change the output of the AND circuit 48 to a logical "0" state, whereby the movable contacts 42-1 of the first relay 42 and the movable contacts 44-1 of the second relay 44 are respectively connected to the second pairs of the stationary contacts 42-22, 44-22. As a result, the communication being performed with the cordless telephone set CT is transferred to the digital telephone set TL. The switch SW-2 is turned ON in order to transfer communication with the digital telephone set TL to the cordless telephone set CT. When the switch SW-2 is closed, the control circuit 8 determines that a command to transfer communication with the digital telephone set TL to the cordless telephone set TL is issued thereby enabling communication with the subunit Y. In this case, a signal sent to the AND circuit 48 from the conversion circuit 4 is kept in a logical "1" state and none of the contacts of the first and second relays 42, 44 are switched.
When the switches SW-1 and SW-2 are operated to transfer communication to the digital telephone set TL from the cordless telephone set CT or to the cordless telephone set CT from the digital telephone set TL, control data required for transfer of communication is transmitted between the main unit X, digital telephone set TL and subunit Y. For instance, when the switch SW-1 is closed to issue a command to transfer communication to the digital telephone set TL from the cordless telephone set CT, the main unit X transmits, to the digital telephone set TL, control data which operates the digital telephone set TL in such a manner that a call is received by the digital telephone set TL. When the switch SW-2 is closed, the control circuit 8 transmits control data for setting the digital telephone set TL to be in a suspended condition.
Such a modification as follows is possible. The movable contacts of the first and second relays 42, 44 are normally connected to the first pairs of the stationary contacts. When the digital telephone set TL answers a call, this fact is detected by the conversion circuit 4, the output of the conversion circuit 4 to the AND circuit 48 is set to logical "0" to cause the AND circuit 48 to output a signal of logical "0" and the movable contacts of the relays 42, 44 are switched to the second pairs of the stationary contacts. In this case, when the switch SW-2 is closed to transfer communication to the cordless telephone set CT from the digital telephone set TL, the control circuit 8 transmits control data to the conversion circuit 4, causing the circuit 4 to output a signal of logical "1" to the AND circuit 48, whereby, the output of the AND circuit 48 is set to a logical "1" state to switch the movable contacts of the relays 42, 44 to the first pairs of the stationary contacts.
The constitution of the subunit Y shown in FIG. 1 is well known and comprises an antenna 20 for transmitting and receiving control data and audio data to or from the main unit X; a receiver 22 for receiving and demodulating a signal from the antenna 20 and separately extracting encoded control data and audio data; a codec 24 for decoding the audio data from the receiver 22 to reproduce a reception signal from a loud speaker 26 and for encoding a transmission signal applied to a microphone 28 to transfer this encoded signal to a transmitter 30; the transmitter 30 for modulating the encoded transmission signal and transmitting this signal from the antenna 20; and a control circuit 32 for controlling operations of the receiver 22 and the transmitter 30, for controlling the termination and origination of call in response to the reception of control data from the receiver 22, for causing received display data to be displayed on a display device 34, for supplying control data inputted from a keypad 36 to the transmitter 30 and for causing the control data on the display device 34.
In the case where data is sent to the digital PBX from the cordless telephone set CT, control data and audio data to be transmitted from the subunit Y are first encoded by the codes 24, modulated by the transmitter 30 and then transmitted as a radio signal from the antenna 20. The transmitted radio signal is received by the antenna 12 of the main unit X and is then supplied to the receiver 14. In the receiver 14, the received data is decoded to separately extract control data and audio data. The extracted control data is given through the control circuit 8 to the protocol conversion circuit 4 as the inherent control data. The audio data from the receiver 14 is sent to the data transmitting/receiving circuit 2. The protocol conversion circuit 4 converts the inherent control data given from the control circuit 8 into the control data specified by the protocol of the digital PBX by means of using the look-up table stored in the ROM 6. Then, the data transmitting/receiving circuit 2 sends the control data from the protocol conversion circuit 4 and the audio data from the receiver 14 to the PBX line.
Therefore, the cordless telephone set CT can be connected to any one of digital PBXs in different protocols by preparing, for each of the digital PBXs of different protocols, a protocol conversion circuit 4 comprising a ROM 6 storing a look-up table between the control data specified by the protocol of the digital PBX to which the cordless telephone set CT is to be connected and the inherent control data of the cordless telephone set CT and a data transmitting/receiving circuit 2 constituted corresponding to the number of digital PBX lines to transmit or receive control data and audio data, and by providing the main unit X with the protocol conversion circuit 4 and the data transmitting/receiving circuit 2 in correspondence with the digital PBX which the cordless telephone set CT is to be connected.
In the cordless telephone set explained with reference to FIG. 1, both or any one of the control circuit 8 of the main unit X and the control circuit 32 of the subunit Y are realized by means of microcomputers and therefore it is possible to add various functions to the cordless telephone set thereby realizing a multi-functional and easy-to-use cordless telephone set by programming these microcomputers as required.