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Phone In Use Indicator(2N2222)

2016-02-13 22:41  
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This article briefly describes the Phone In Use Indicator (2N2222). This principle is easy to understand, but also very practical. Depth understanding of circuit elements, can be more effective to grasp this principle. Do you know the circuit, for example, can understand and buy these components: 2N2222,2N4360 .

With this circuit mounted in or near every phone in the house, it will allow users to know if the phone is being used and not to pick up the phone. When a phone is taken off hook, the voltage across the tip and ring terminals drops to 10 volts or less. This will cause theFET(2N4360) to turn on and also turn on the transistor (2N2222). When the transistor turns on it will allow current to flow through theLEDand make it light. A blinkingLEDcould be used to make the effect better.


Figure 1 



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