Compander for TDM telecommunication system

Claim 1

A compander for a TDM telecommunication system wherein a transmitting terminal, having means for periodically sampling the signal amplitudes on a multiplicity of incoming signal channels, is connected via a communication link with a receiving terminal having means for distributing arriving amplitude samples to a multiplicity of outgoing channels, comprising: synchronized timing means at said terminals for generating respective sequences of 2 n isochronous clock pulses during a coding interval occurring at least once per sampling period, with n = m + p, the number 2 n representing a multiplicity of quantizing amplitude levels subdivided into 2 m groups of 2 p amplitude levels per group; a first signal generator at said transmitting terminal and a second signal generator at said receiving terminal controlled by said timing means for respectively producing, during each coding interval, a first and a second reference voltage each following a quasi-exponential curve divided into 2 m straight segments each coinciding with a series of 2 p clock pulses; a plurality of coders at said transmitting terminal, one for each incoming channel, each including a first comparator connected to said first signal generator for receiving said first reference voltage and further connected to the respective incoming channel for receiving amplitude samples to be coded, each of said coders also including a first binary counter for said clock pulses connected to said timing means for zero-setting at the beginning of each coding interval and further connected to said first comparator for halting its count whenever the instantaneous magnitude of said reference voltage equals the amplitude sample to be coded; multiplexing means at said transmitting terminal for delivering respective binary codes, representing the counts of the several first counters thereof, in interleaved relationship to said communication link during each sampling period; a plurality of decoders at said receiving terminal, one for each outgoing channel, each including a second binary counter for said clock pulses connected to said timing means for zero-setting at the beginning of a decoding interval of the same duration as said coding interval; and demultiplexing means at said receiving terminal for distributing arriving binary codes from said communication link to said decoders during each sampling period, each decoder also including a second comparator connected to said demultiplexing means and further connected to said second counter, output means including a normally closed sampling gate inserted between the respective outgoing channel and said second signal generator, said sampling gate being controlled by said second comparator for opening at the instant when an arriving binary code matches the count of said second counter to pass the instanteneous amplitude of said second reference voltage. 21