A symbology input device typically uses a sensing beam to read a symbology, such as a bar code, which consists of alternating areas ("bars") having differing characteristics to which the beam is sensitive. The bar code, or other symbology, can be used to store information or commands which are addressed to other devices. After sensing the symbology, the input device then receives and interprets the fluctuations in the returning sensing beam that are caused by the symbology. For example, it is known in the prior art to read symbology by means of a hand-held wand which makes contact with the surface on which the symbology is printed and reads the symbology by means of a beam of light. It is also known to use a non-contact scanning device to cause a beam of light to scan across an area containing a bar code. Such input devices typically transform the reflected scanning beam to an electronic form for decoding.
Decoding includes both 1) interpreting the received reflected signal as a representation of the alternating characteristics of the symbology and 2) checking the representation and producing the symbol or symbols being represented by the symbology. The decoding function is generally performed by a reader device which can include a microprocessor and associated memory devices. The memory devices are used to store the program under which the microprocessor operates and tables of data which contain the correspondence between representations and the represented symbologies.
In use, the scanning device can scan symbols faster than the symbols can be decoded and stored. In applications where a large number of symbols are read within a short period of time, the efficiency of the operation is materially degraded because the operator often must wait after a scan for the reading device to catch up, or data is lost.