GB1317756A - Keyboard terminals - Google Patents

Abstract

1317756 Keyboard terminals INTERNATIONAL BUSINESS MACHINES CORP 30 July 1970 [29 Sept 1969] 36885/70 Heading G4H A keyboard terminal comprises keys 10 each of which when actuated causes a respective trigger circuit 42 to generate a trigger signal, latch circuits 44 each associated with a respective one of the trigger circuits and effective to provide an output signal when triggered by the associated trigger circuit and encoders 45 which are capable of encoding a succession of the output signals despite an overlap in the timing of the corresponding trigger signals. The circuit shown in Fig. 5 is incorporated in each module 15 associated with a respective key 10 and each encoder comprises an array of pins connected to an etched wire pattern, Fig. 6 (not shown), which forms a bus 11. The depression of a key moves a magnet (58), Fig. 11 (not shown), towards a piece of indium antimonide (59) thereby changing its resistivity and supplying a voltage change to the pin connections thereby providing a unique 8-bit coded signal for each key. The coded signals address a data store 12 which supplies a B.C.D., ASCII or EBCDIC coded signal representative of the actuated key. Control timing and interlock circuits 14 transfer the coded signal to a register 17 for temporary storage and for connection to a printer (not shown) via a bus 18. If a high speed display is used instead of a printer, the bus 16 is connected directly to the display. The provision of the latch circuits 44, the output pulses from which do not overlap in spite of overlap of the output signals from trigger circuits 42, ensures that characters are not lost. Instead of using a magneto resistive effect in the encoders, a capacitative bridge, inductive coil, Hall effect or light emitting circuits may be used.