This circuit is used to monitor the situation of a home, even from remote locations.ie, it is used for off-site monitoring. When the person at home needs to go out, its enough to switch on the listener which is connected with the Telephone. The listener will be connected to an amplifier. After going away from the home, if the home situation is needed to be checked, then its just enough to call the telephone number. When the telephone rings, it switches of a relay, and a MIC. The MIC keenly listens the sounds in side the home and sends it to amplifier. The amplifier amplifies the sound and sends it to the person who makes the call.
The printed circuit board of the circuit is also given above.