Phone Usage Indicator Circuit Schematic Diagram


This circuit is very useful to display phone usage indicator. When the phone is used, the transistor Q1 will be active and LED S2 turns on. On the contrary, when the telephone is not being used, the transistor Q1 will be OFF and transistor Q2 will be ON. This will cause the LED D2 OFF and LED D3 ON. Here is the schematic :

Phone Usage Indicator Circuit Schematic

Phone Usage Indicator Circuit Diagram

Components :
Bridge diode D1 : 2A
Resistor R1 : 3.3k ohm
Resistor R2 : 22k ohm
Resistor R3 : 33k ohm
Resistor R4 : 4.7k ohm
Transistor Q1-Q2 : 2N3392
D2 : Red LED
D3 : Green LED

Estimated price : $3


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