| 摘要 |
PURPOSE:To monitor the collision of incoming and outgoing calls surely and to attain the incoming call priority control, by detecting the presence of an incoming call for a prescribed time, after an automatic calling device closes the line loop for dial transmission. CONSTITUTION:A high-order controller, at the start of calling informs a trunk number used in bidirectional trunks 2-1-2-n to a calling control section 12 of an automiatic calling circuit 7, and connect a subscriber line to the circuit 7 via a switching circuit 3-1. The control circuit 12 holds the timing for the guarantee of restoration of advanced connection, and forms a line loop for automatic calling. During this time, an incoming and outgoing collision preventing circuit A9 monitors the incoming call. After the closing of the loop, an incoming and outgoing collision preventing circuit B10 detects the incoming call by the monitoring of the inversion of polarity of the line for a prescribed time. When the circuits A9, B10 detect the incoming call, the high-order device informs the abolishment of the calling due to automatic calling to the subscriber. The transmission of dial signals and the detection of the remote subsceiber response are executed by circuits 8, 10 conventionally. |
