( DC 9V)
OPERATION : This simple transmitter transmits telephone conversation to a remote FM radio. The antenna was intentionally left out in order to limit the transmission range. The circuit does not need any battery to operate. It taps energy from the telephone lines & will start transmission once the telephone is in use.
The radio frequency can be adjusted by tuning the trimmer cap. The frequency falls within FM broadcast band which ranges from 88 ~ 108 MHz.