PURPOSE: To simplify the function of a toll center test board to be tested by slaving each toll center test board to be tested completely depending on a toll center test board in a remote test to be conducted by controlling the toll center test boards to be tested from a test board installed to a centrallized maintenance center via a telephone exchange network.

CONSTITUTION: A function as a slave device of a test board DESK of the maintenance center is provided to an adaptor ADAPTER for test installed to a toll center to be tested, a test item in the instruction form is transmitted to the toll station ADAPTER via an advanced data link controller ADLC and a digital interface controller DLIC from the maintenance center test board, the device ADAPTER executes the instruction and also transmits the response to the maintenance center test board. The test adapter installed to each toll center to be tested is simplified by the compelled system procedure depending on the semi- duplex communication like this and the communication with the maintenance center is also simplified.