GB1519779A - Apparatus for control of equipment via a single transmissions path - Google Patents

Abstract

1519779 Signal transmission system; acoustic remote control A W BUTLER 2 March 1976 [3 Dec 1974] 52153/74 Headings G4H and G4F Apparatus for control of equipment via a single transmission path includes (i) a transmitter comprising a clock 4, a shift register 3 and logic 8-21 which convert a parallel binary signal 2 into a serial signal 18 wherein each 1 (0) bit in signal 2 is represented by a pulse of duration greater (less) than half the period of clock 4, and (ii) a receiver comprising a shift register 22 to which signals 18 are applied under the control of a monostable 24 which produces an output sampling pulse of length equal to half the period of clock 4. As described, the pulses 5 from clock 4 have a mark/space ratio of 1 : 2. When there is data 2 to be transmitted, a signal 9 from interface 8 places a 1 in the last stage of register 3, the output 14 from which sets flip flop 10 and enables gate 17; output 11 from flip flop 10 enables register 3 and AND gate 21. Each O level from clock 4 triggers a monostable 19 having a 1 : 2 mark/space ratio. Thus gate 21 is enabled once (by clock 4) for a O output from register 22 and twice (by clock 4 and monostable 19) for a 1 output. Therefore, signal 18 consists of the initial 1 signal, followed by encoded 0 and 1 signals, followed by 0 signals. In an alternative embodiment, flip flop 10 may be omitted. In the receiver, a gate 23 is enabled by the 0 output from register 22 until the initial 1 signal reaches the last stage. Monostable 29 is triggered on the rising edge of each pulse 19 and its falling edge enters the pulse into register 22 (i.e. the pulse length is sampled and stored). A clear signal 28 is applied to register 22, until the first pulse of signal 18 is received, by a retriggerable monostable 24 of period greater than that of clock 4. The data eventually stored in register 22 is removed in parallel 33 and applied to an interface 36.