Abstract: A digital communication system having a universal backplane bus and a plurality of interface circuits connected to remote peripherals, for effecting bidirectional communication of information signals between the remote peripherals via the bus, as well as the exchange of message signals between local control circuitry resident on individual ones of the interface circuits. Each interface circuit has a digital time and space switch for transmitting the information signals in PCM format between the remote peripherals and the universal bus, under control of the control circuitry resident on respective ones of the interface circuits. An HDLC controller is provided on each of the interface circuits for controlling the exchange of message signals between the local control circuitry resident on the respective ones of the interface circuits.