| 摘要 |
PURPOSE:To obtain easily a terminating ringer synchronized with an incoming signal by switching a low-frequency oscillator to connect it directly to a channel synchronously with the incoming signal. CONSTITUTION:In case of incoming, the low level is inputted to an input terminal 11. If the incoming signal of 16Hz is inputted between input terminals 1 and 2 at this time, a light emitting diode 8a of a photocoupler 8 emits light, and a signal synchronized with the incoming signal is outputted from a photo transistor TR 8b of the photocoupler 8. Consequently, a switch of a switch element 5 is driven by the output from a logic element 10. Thus, a signal of 500Hz is sent from a low frequency oscillator 7 to an output terminal 6 while an input terminal Y and a common input/output terminal Z are connected. In case of outgoing, the switch 5 is not driven though the light emitting diode 8a of the photocoupler 8 emits light when the high level is inputted to the input terminal 11. Consequently, the resonance for dial outgoing is prevented because the signal of the low-frequency oscillator 7 is not transmitted. |
