PURPOSE: To obtain a test board that never troubles terminal users by making an interruption when a circuit to be tested is in a free state at the output point of a picture center.
CONSTITUTION: Between public telephone network 2 and incoming trunk device 9, circuit switching part 17 is installed to perform switching operation under the control of controller 13. Circuit switching part 17 functions to disconnect incoming trunk device 9 from public telephone network 2 and to connect testing terminal part 16 to incoming trunk device 9. The operator assigns a circuit to be tested from circuit assignment part 15. Controller 13 puts circuit switching part 17 into operation when the corresponding circuit is free. Therefore, a circuit in use is never interrupted and terminal users are never troubled neither.
OOGOSHI MASAE
FURUKAWA KOUJI
NIPPON TELEGRAPH & TELEPHONE