PURPOSE: To take a trunk test easily and efficiently without using a terminal telephone set by making sure of calling and dial and trunk tones by control information from a central controller.

CONSTITUTION: As the test command is inputted from typewriter TYP, central controller CC sends control information for the confirmation of calling operation and dial tone DT to interface circuit 1 of trunk testing device TAT via trunk controller TKC. Device TAT holds the control information in holding circuit 2 and performs calling operation by calling circuit 3. When dial tone DT from originating circuit 4, test result sending-back circuit 5 sends it back to controller CC via controller TKC. Controller CC judges the test results and, when it is judged that the result is normal, sends control information on dial transmission of one number to device TAT via controller TKC to take the next test.