| 摘要 |
PURPOSE:To connect a manual holding circuit to a telephone switchboard via a carrier device by preventing the arrival of a new call from an originating telephone switchboard by a blocking-signal sending function on the basis of fault information from a telephone switchboard at a carrier device or incoming side. CONSTITUTION:Electronic detectors A-DECT of signal converters SC1-SC24 detect an incoming call by closing a loop on a call line by an originating telephone switchboard, and consequently a common control signal processing circuit COM- CONT is put in operation through a corresponding terminal M. Through this operation, a start signal sent from a carrier multiplexing circuit MU through the multiplexing circuit SIG-MUX for control signals of a carrier multiplexer MUX. When an answer signal is sent from an incoming telephone switchboard, the circuit COM- CONT is put in operation through the circuit SIG-MUX to send a signal from a corresponding terminal E to a relay DRV, and then an electromagnetic relay ANS is operated to switch the contact ans of the relay ANS. As a result, the polarity of a loop monitoring circuit for channels is inverted to prevent a failure in recovery from the fault of a manual holding circuit. |
