Abstract: A time division digital transmission system in which data are transmitted in the form of pulses grouped in multiplex words in time slots forming a recurrent frame. The invention relates more particularly to facilities in transmission line station for sampling from or introducing into the frame data words occupying certain time intervals in the frame. Each station comprises at least a multiplexer, a demultiplexer and a reception time base for restoring from the incoming frames and their framing words the time intervals and addresses of the said incoming frames, so that the component channels can be multiplexed and demultiplexed. Each station further comprises a local time base capable of producing local frames having framing words and the rhythm of which is controlled by the incoming signals, but which is able to oscillate freely in the absence of such signals.