Communication system for the transmission of information between two terminal stations by pulse code modulation

Claim 1

A time division multiplex communication system including two terminal stations connected together through two transmission paths, said stations being substantially identically constituted for transmitting information by pulse code modulation, said stations each having an encoder for information received on incoming channels to be transmitted to the other station, said encoder being coupled to the incoming channels through a time division multiplex device for sequentially providing samples to the encoder representative of the information on the different incoming channels, and a decoder for information received from the other station and to be sent on outgoing channels, said decoder being coupled to the outgoing channels through a time division multiplex device for sequentially providing signals to the respective outgoing channels representative of the decoded information samples received from the other station, said multiplex and demultiplex devices each operative at their own clock frequency, said clock frequency representing a sampling frequency for the incoming and outgoing channels, respectively, said time division multiplex communication system further comprising: A. a signal generator for each station adapted to be connected to at least one of the incoming channels of that respective station; B. supervision means for each station for comparing a received test signal with a reference, for connection to at least one of the outgoing channels of that respective station; C. a digital store for each station, each digital store coupled to the output of said encoder, and the input of said decoder for that respective station; and D. a control unit means for each station for controlling its respective digital store, means associated with each control unit for sensing the respective sampling frequency for said multiplexed incoming channels, means for sensing the sampling frequency for said multiplexed outgoing channels, said control means containing means for writing a sampled signal from said signal generator into its respective store at a frequency which is a submultiple of said sampling frequency of the incoming channels and means for reading the stored signal from said store and applying it to said decoder at a frequency which is substantially equal to said submultiple frequency and in synchronism with the sampling frequency assoicated with the outgoing channels, said control unit further comprising a logic circuit means for delaying readout of said digital store an integral number of frame intervals when a time interval between consecutive writing and reading intervals becomes less than a given minimum duration, whereby overlapping of these intervals is prevented.