The work of the circuit when press switch S1 will have the electric current flows through R1 go to pick the electric charge at C1 at a pin B of Q1 as a result, will have electricity pressure then until make Q1 work.
When Q1 work Q2, as a result work with, be make have current flow through pin E come out the way pin C of , Q2 change R4 go to a loudspeaker. By C2 will charge when C2 charge with full speed ahead pin B of Q1 have low voltage poverty Q1 do not work. The Q2 stop work with make C2 disgorge load change R4, SP1 and R3 down ground poverty voltage at a pin B tall go up, as a result make Q1 begin the work again and make Q2 work, then born the sound at SP1. Which Q1 and Q2 work until quickly cause frequency at a loudspeaker. When we liberate switch S1 as a result cause C1 begin discharge. It make voltage at pin B of Q1 be down. It make the frequency has that quietly, then until switch off go to.