Circuit diagram of adding visual judgment function to phone ringing

HA868 P/TSD telephone, connect a 10k ohm resistor between C301 and R301 . The other end of the resistor is connected to the positive terminal of the 1N4004 diode, and the negative terminal of the diode is connected to the positive terminal of the LED. As shown in the dotted line part in the figure. When the telephone is working, the current passes through R201 to make the LED light up. Due to the reverse bias of 1N4004, the current flow to the ringing circuit is blocked, and the modified part has no effect on the working indicator light. When ringing, the ring current is rectified by C301, 10K resistor and 1N4004 diode, and forms a loop through LED and D304. The LED flashes and glows. Since the shunt of the ringing indication is very small, the ringing has no significant effect.

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