hii i m bhavani i want advantages and disadvantages of electronic watchdog circuit.

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plzzz give the information regarding advantages and disadvantages of electronic watchdog circuit.

The circuit comprises a transmitter unit and a receiver unit, which are mounted face to face on the opposite pillars of the gate such that the IR beam gets interrupted when someone is standing at the gate or passing through it. The transmitter circuit is built around timer NE555 which is wired as an astable multivibrator producing a frequency of about 38 kHz. The infrared (IR) beam is transmitted through IR LED1.