The heart of this anti-theft alarm of the whole circuit is the operational amplifier IC CA3140 (IC1), configured as a comparator. The two inputs (inversion and non-inversion) are assigned to pins 3 and 2 of the operational amplifier, respectively, and the output is obtained from pin no 6. Here IC2 (timer IC NE555) is used as a monostable multivibrator. The timing component of the anti-theft burglar alarm is R5, VR1 and capacitor C2 with the value given in this circuit diagram allows the timer time to be approximately 1 minute.
For the audio section, IC3 is used as an alarm tone generator with a built-in oscillator. Finally, the output is obtained from pin 3 of IC3 and is amplified with transistor T1 to obtain the desired level and finally fed to the speaker for output.