| 摘要 |
PURPOSE:To drive an audio display circuit common to respective circuits by the output of an incoming detecting circuit which uses a photocoupler and provides a visual and an audio display at the time of a power failure by providing a visual display circuit equipped with a light emitting diode and the incoming detecting circuit and operating those circuits at the time of incoming to them. CONSTITUTION:A current flows through a relay P in a normal state, i.e. while no power failure occurs and a relay conact P0 is broken. If there is incoming to a circuit 8 in said state, the current flows to the light emitting diode LED through resistances R1 and R2, a capacitor C, and a diode D0 to obtain the visual display on the light emitting diode D0. Then, the incoming signal is further applied to the photocoupler PH through diodes D, D1, and D2, resistances R3 and R4, and a capacitor C2. If a power failure occurs, no current flows to the relay P and the relay contact P0 is made, so the positive side of a source battery 13 is connected to an oscillation circuit OSC through the relay contact P0. If there is an incoming signal is said state, the photocoupler PH turns on as if there were no power failure, and the negative side of the source battery 13 is connected to the oscillation circuit OSC. |
