| 摘要 |
PROBLEM TO BE SOLVED: To obtain a ring trip circuit that detects a trip, without being affected by fluctuation in a call signal source, a loop resistance and a leak resistance or the like of a subscriber line and switches a relay, while taking a delay of the relay into account in the case of switching the relay at a zero cross point of a call signal in order to prevent an overvoltage at relay contact changeover. SOLUTION: An optical transmission section 7 is provided with a current limit resistor 14, whose one terminal is connected to the other end of a lease resistor 2 for current detection control, a Zener diode 15 whose cathode is connected to the other terminal of the current limit resistor 14, a light emitting diode 7a whose anode is connected to the anode of the Zener diode 15 and whose cathode is connected to the other end of the lease resistor 2, and a diode 16 whose cathode is connected to the cathode of the Zener diode 15 and whose anode is connected to the cathode of the light emitting diode 7a. Since the ring trip circuit can detect trips without being affected by fluctuation in a call signal source, a loop resistance and a leak resistance or the like and generates a reset signal by taking a delay time of a relay into account, it is possible to disconnect the relay at a zero-cross point of the call signal and overvoltage at relay contact changeover can be prevented. |
