Abstract: A communication switching station includes a digital switch and a sub-rate interface circuit. The switch has signal terminals including inputs and outputs, and switching circuitry, adapted to operate at a first rate, operatively connected between the inputs and outputs. The sub-rate interface circuit includes a first signal terminal operatively connected to at least one of the signal terminals of the first signal terminal and the second signal terminal, the programmable circuitry being operative at a second rate that is lower than the first rate.