A switchboard control system in which a plurality of switchboards are connected to a time division exchange and controlled by the time division exchange. A speech signal and a control signal (a signal for key information, display information, subscriber number information and other information necessary for the exchange operation by a switchboard operator), which are delivered and received by each switchboard and the time division exchange, are transmitted together by a common transmission line on a time-division-multiplexed basis. On the side of the system toward the switchboards are disposed a position controller, by which the signals are multiplexed and separated and the common transmission line and the switchboards are interconnected. For delivering and receiving the signals, common channel signalling equipment is connected to the time division exchange and remote channel signalling equipment is provided in the position controller. Between the signalling equipment, the control signal is transferred via the common transmission line and, between the remote common channel signalling equipment and each switchboard, it is transmitted via a control signal line comprising a common bus separate from a signal line for the speech signal.