电路图![]() 零件: C1 0.47uF 250V Capacitor R1, R2 10K 1/4 W Resistor R3 1K 1/4W Resistor D1, D2 20V 1/4W Zener Diode D3 1N4148 Diode Q1 2N3904 NPN Transistor or 2N2222 U1 4N27 Opto Isolator RELAY Solid State Or Regular Relay (See Notes) MISC Case, Wire, Board 注释 1. You may need to use a lower voltage zener for D1 and D2. 2. Be very sure that you have not accidentally connected 120V to the phone line when building and installing this circuit. 3. You can use a regular relay instead of a solid state relay, but the arcing accross the contacts may destroy it pretty quickly. |
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电话振铃指示灯设计

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