PURPOSE: To decrease the number of lines and to simplify a writing work by using a means which can supply an opposite office number through a keyboard, etc., and detects and catches the idle state of a TS for the reception of the opposite office number and a function which informs the TS number of its own office to the opposite office and setting the bidirectional time division channels at both offices.

CONSTITUTION: A terminal equipment 18 includes a compression circuit 20 putting an external clock and the data (voices) synchronizing with said clock onto the optional TS of a PCM-HW, an expansion circuit 21, an algorithm executing function 22 for the connection of calls, and a selection circuit 23 for the selection of an optional TS. A PCM-HW controller 19 consists of a clock generator 25 and an FSX generator 26 and produces the reference signal of a PCM-HW 27. At the transmitter side the idle state is checked and caught for the receiving TS of the opposite office when the opposite office number is supplied through a keyboard 24. Thus a channel can be set between both offices and the connection is secured for the terminal equipments of 26 offices at the maximum just with a single piece of PCM-HW 27.