GB1235481A - Information transmission system - Google Patents

Abstract

1,235,481. Signalling by audio-frequencies. BRITISH AIRCRAFT CORP. Ltd. 12 March, 1969 [19 Dec., 1967], No. 57589/67. Heading G4H. [Also in Division H4] In a system for signalling between a central station and a number of remote gun stations by radio telephone or over telephone lines the central station has a microphone and an encoder adapted to accept a decimal input and produce a binary coded output the "1" and "0" bits of which are represented by two audio-frequency tones, means being provided to transmit either the output from the microphone or the output from the encoder and means at the receiver to reproduce either speech or the original decimal input. The decimal input, from a computer for a keyboard, is applied to the encoder and a switch passes it to the transmission circuit. The signals are gated into a shift-register in the encoder under the control of clock pulses. A counter gives a signal when the message is complete to switch the transmission back to the microphone. At the gun station the two frequencies are separated by filters, the output of the "1" filter being applied to a call recognition circuit which enables the decoder. This comprises a shift register into which the incoming serial signals are shifted under the control of clock pulses derived by combining the outputs of the "1" and "0" filters. The output of the shift register is recoded from binarycoded-decimal form into decimal form and displayed on indicators showing the azimuth and bearing to which the gun is to be laid. Speech signals are reproduced on a speaker.