| 摘要 |
PURPOSE:To obtain a signaling converter which is adaptive to an analog exchange with a manual holding function by providing a current detector which detects the backward current of a loop circuit. CONSTITUTION:When an actuation signal is sent from a calling subscriber side, a contact 5 is made to flow a backward loop current, so the current detector 6 sends out a 0 level to a microprocessor MPU and when the side of the analog exchange 1 answers, the current flows reversely, so the current is not detected and a 1 level is sent out. Further, the current is inverted again in direction on normal on-hook operation, so the current is detected and the 0 level is sent to the MPU. When on-hook operation is performed in manual holding mode, no loop current flows, so the current detector 6 still sends the 1 level to the MPU as well as during a talk and then the MPU checks signals from a blocking detector 4 and current detectors 3 and 6 to discriminate normal on-hook operation and on-hook operation in manual holding mode. |
