| 摘要 |
PURPOSE:To enable to detect the presence of failure, by providing the photo coupler with the reference voltage set circuit and detecting the current flowing to the detection circuit when the drive circuit is not driven. CONSTITUTION:Diodes D1, D3 and D2, D4 are branched and connected to scanned circuits respectively which are provided corresponding to the subscribers, via current limit resistors R1 and R2. The D1, D2 are connected to the drive circuit for current switching and other diodes D3, D4 are connected to the reference switching and other diodes D3, D4 are connected to the reference voltage set circuit and the detection circuit T3 common to a plurality of scanned circuits. The presence of failure can be detected by using the photo coupler P for the reference voltage set circuit and detecting the current flowing to the circuit T3 when the drive circuit is not driven, with the photo coupler P. |
