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Phone Message LED Flasher Circuit

2014-12-23 06:57  
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This is a circuit ofphonemessageflasher, an alternative way to get alarmed when there is an incoming call. When the phone rings, high line voltage will be detected by A differential amplifier with hysteresis (Q2, Q3, and Q1). This action will turn on multivibrator Q5/Q6, Q4. The LED will flashed via Q7. When thephone linevoltage drops to less then 9V, the Q2 and Q1 will be turned off, which indicates an off hook condition.This circuit flashes an LED to indicate that your phone rang during your absence. A differential amplifier with hysteresis (Ql, Q2, and Q3) detects high line voltage (ringing), which turns on Q4, multivibrator Q5/Q6, and flashes the LED via Q7. Ql and Q2 remain on until the phone-line voltage drops to less than 9 V, which indicates an off-hook condition.This is opposed to the light chaser circuits that can flash four or more. Of course, the simplest LED flasher is simply to use a flashing LED.

Phone Message Flasher