A method for jam and catching of a public switching center opening extends in a private branch exchange

摘要

A test connection is established from the test-board at the public exchange which is connected through a board switching set to the switchboard of the public exchange, controlled by the central computer. The information from the test-board is fed to the control unit in coded form from which the test target is recognised. The output circuit is then connected to the selector in the private exchange with a follower set which carries out a line occupancy check and stores the figure of the number called. The response to a free line is a signal which releases the stored number sequentially under control of the central unit. The central control unit of the private exchange receives the test instructions through units in the public exchange and the private exchange which are permanently connected.