The gate N1 acts as a buffer for strengthening the signals from the condenser microphone. The inverter N2 with its associated components forms a radio frequency oscillator in the FM region. The varicap diode BB109 is used for frequency modulating the audio signal to the carrier wave generated by the oscillator. Inverters N4 t0 N6 are used to drive t
he antenna. As the N4, N5, N6 are connected in parallel their effective output impedance is very less and can easily drive the antenna.