Capacitor C5 and potentiometer R12 figure out the frequency of the output signal at pin number 3 of IC1, the 555oscillator. The output signal is differentiated by C3 and C4 before it’s input to the base of power transistors Q1 and Q2 through diodes D1 and D2, respectively. The signal from IC1 is adjusted to 120 Hertz, because the flip-flop created by transistors Q3 and Q4 splits the frequency by two.
To reduce switching transients as a result of the fast switching of Q3 and Q4, capacitors C1 and C2 filtering the input to the base of Q1 and Q2 . Electrical power for the inverter get from an car’s 12 Volt system or from a electric battery. The voltage will be regulated by IC2 ( 7812 regulator). LED1, connected over the 12 Volt input, enable you to indicate when electrical power is being given for the inverter circuit. The pilot lamp, LMP1, displays the state of output power.