Sequential encoding and decoding apparatus for providing identification

Abstract

An encoder for manually or automatically providing a sequence of identifier signals and a decoder for same, in a remote dictation system. A pair of control lines (10, 10' and 11, 11') carry the identifier signals which are in part identical to signals used to control dictation recording functions of the remote recorder. A sequential counter (31) and a matrix of switches (32) provide an automatic sequence of signals to a set of transistors (15-18) and diodes (19, 20, 22) which establish the control line voltages. These devices are alternately connected (70-75) to shift registers (61, 62) which accept keyboard signals entered from a keyboard (60). Timing circuitry (65, 66, 68, 69, 99, 117) controls the shifting of keyboard signals in and out of the registers. A combination of comparators (150-153) and gates (170, 171) decode the control line voltages and provide inputs to decoding (169, 172, 176) and timing (191, 195) circuitry which provides a binary number to a memory device (250). The occurrence of special, non-numerical, signals is detected by special gates (227, 237). Also shown is verification apparatus comprising a pair of digital comparators (310, 325) which will prevent operation of a recorder unless the identifier signal corresponds to a predetermined valid signal stored in a memory (311).