- Asimple telephone transmitter circuit that is ideal for transmitting the telephone conversation through small distances.The circuit is very simple and uses only few components.
- The entire circuit can be easily included in the telephone itself or in the junction box.The circuit is powered from the telephone line itself.
- The transistor Q2 is wired as a a Colpitts oscillator to produce oscillations in the FM transmission band.
- The audio signal from the telephone line is coupled to the the base of Q2 to obtain the frequency modulation.The LED D1 acts as a power on indicator.
NOTES:
- Any radio frequency PNP transistor like A933 can be used for Q2.
- For L1 make 8 turns of 0 .6mm dia enameled copper wire on a 3.6mm dia steel bolt.
- For antenna use a 15cm long 0.6 mm dia copper wire.
