Electronics phone locker

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Phone locker
Building a electronics phone lock is so easy. Any one can build it their home by the help of few electronics components. The phone locker is very simple to construct and can be housed in a small plastic cabinet of the size of a match box. Only you have to connect it in the phone as shown in the circuit diagram.
PART LIST
PARTS LIST Telephone     -
Resistor     220 K
LED     GREEN
LED     RED
Capacitor     1 400V
Switch     SP

Description
When the handset is removed from cradle of the telephone, one of the LEDs lights up, indicating that the phone is not dead. And on dialling required number, the LEDs start flickering, indicating that the number is being dialled. This way one can  detect whether someone is misusing the phone from the wires going outside the house.

Once the ringing tone reaches the caller and the caller lifts his own handset, the other LED lights up indicating that the call is matured. For differentiation, two different coloured LEDs have been used. This happens due to reversal of the polarity of voltage in the exchange wires. When switch is moved to ‘off position, the capacitor is introduced in the circuit. In this position the phone becomes for the outgoing calls but the incoming calls regularly come through the capacitor, i.e. you can listen to the voice of the caller but they cannot listen to your voice. So, to enable the incoming calls, the switch should be moved to ‘on’ position and the conversation made as usual.

In this way you can build the electronics phone lock in your home.


..Read more http://electronicsproject.org/phone-locker/
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