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Simple Telephone Transmiter

2015-01-08 18:06  
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This circuit is a circuit diagram of a simple transmitter, but very useful circuit which can be used to transmit telephone conversations. When the telephone receiver on the hook to the line voltage of about 48 volts. R7 preset is adjusted to 24.7 V between the cathode of D2 and ground. In voltage Zener diode D2 will be in the breakdown and the transistor T1 will conduct. This makes the transistor T2 OFF. When the receiver off the hook, the line voltage drops to about 11 volts. This makes the transistor T1 is OFF and then ON the T2. The T2 is switched ON condition will give way to the DC transistor T3 which is used in the FM transmitter. Transistor T3 is the cable as a common emitter radio frequency oscillator. In simple words the transistor T2 functions as ON / OFF switch for this oscillator. Modulated signal will be available to collectors of transistors T3 and id fed to the antenna signal through a capacitor C5. The following is a schematic drawing:

telephone transmitter circuit1 Simple Telephone Transmiter

To L2 makes 3 changes of 21 SWG enamelled copper wire on a plastic 12 mm.
For the antenna, use a 1 meter insulated copper wire. Capacitor C3 can be 50pF trimmer.

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