Oscillator: Oscillator is a device which can produce high frequency oscillation. (i) Labelled Circuit diagram : (ref. image) (ii) Working: As the key K is pressed, the electrical oscillations begin in the L 1 −C 1 circuit or tank circuit. Inductance L is properly coupled with L 1 , there an induced e.m.f. is produced in L and its direction and magnitude both are changing. Thus, a flucting collector current is produced due to the flucting base potential, which helps the electric oscillations in tank circuit and hence an oscillation of conduct amplitude is produced in L 1 −C 1 circuit. The energy is fulfilled by the battery.