When the supply voltage is applied to the given schematic, the current flowing through R and P begins to fill. When the voltage of C reaches a certain level (0.6-0.7 V), the transistor passes through conduction, causing the relay to magnetize the coil. By magnetizing the relay coil, the pallet is pulled and the contacts are switched to start the lamp.
When B is pressed, the lamp goes out when C is drained. If the supply voltage of the power source continues, the lamp lights up again after a period of time from B to the time of elimination.
Duties of the inactive members:
R Resistance: When the value of the potential is zero, protect the transistor’s base against over-current.
Pot (P): Sets the charging time of the capacitor. That is, we can determine the delay time.
Capacitor (C): Allows the circuit to start operating with delay.
Transistor: It drives the relay by passing a higher current through collector-emitter terminals with the small valued current coming to the tip of the base.
Relay: When the coil is energized, it changes the position of the contacts and enables to control of a high-current receiver.
Diode: The high value of the induction voltage generated by the coil of the relay prevents distortion of the transistor. That is, it allows high-value tensions to circulate through the rider’s own bobbin.