Abstract: A data signal transmission control apparatus includes a connection unit for connecting a plurality of first lines and any one of at least one second line that are accommodated in a switching unit between the first lines and the second lines for transmitting a speech signal; a control unit for controlling the connection operation of the connection unit; and an isolation/insertion unit for isolating a data signal, flowing on one of the first and second lines connected by the connection unit, from the one line and inserting the data signal isolated from the one line onto the other line.

Abstract: A data communication system is capable of performing data communication by readily changing the ratio of SCN/SD data and DMA data corresponding to each communication and to individual destination devices. The data communication system may include a first communication device and at least one second communication device, connected to said first communication device via a transmission path, said first communication device notifying a transmission frame format to said second communication device, and said first communication device and said second communication device transmitting and receiving data using said notified transmission frame format.

Abstract: A communication box which operates as a testing and complaint accepting communication unit and which is connected with a workstation which can communicate with a call processor for controlling a digital switch module includes a subscriber line interface connected with a subscriber line from a subscriber line circuit for transmitting/receiving speech signals to/from another telephone connected with one exchange, an inter-office interface connected with an inter-office communication line from an inter-office communication trunk unit for transmitting/receiving speech signals to/from another exchange, and a telephone circuit which connects a head set for talking to allow to select a line of either interface and to call and communicate with either interface under control from the workstation and to communicate or to test a speech condition defined by speech signals monitored at the head set.