| 摘要 |
PURPOSE:To allow a call to be replied without fail even if either a secretary or a manager is absent by using a bridge rectifier circuit and a resonance prevention circuit of a secretary call circuit in a secretary telephone set so as to share the detection of a ring tone start voltage with both the secretary and the manager telephone set. CONSTITUTION:Resistors 22, 27 and a capacitor 26 are selected in a way that a transistor(TR) 28 is turned on only when a call signal is a 16Hz sinusoidal wave inputted to line terminals 1, 2 and rectified and inputted by a bridge rectifier circuit 5 into a resonance prevention circuit 20. When the line terminals 1, 2 receives the 16Hz call signal, the call signal is a rectified signal by the bridge rectifier 5 via a capacitor 3 and a resistor 4. The rectified signal of the call signal passes through the on-state resonance prevention circuit 20 to start two oscillation circuits 7, 41 simultaneously, thereby generating an audio signal, which allows speakers 8, 42 to ring the tone.
|
