please sendbme somebinformation about transistrr based intercom ckt

Description.

Here is a simple but effective intercom circuit that is completely based on transistors. The circuit is based on a three stage RC coupled amplifier. When the pushbutton S2 is pressed, the amplifier circuit wired around T1 & T2 becomes an astable multivibrator and begins to produce the call signals. These call signals will be amplified by the transistor T3 to drive the speaker. When the S2 button is released, the circuit will behave like an ordinary amplifier and you can talk to the other side through it.

To construct a two-way intercom, make two identical copies of the circuit shown below and connect it according to the given connection diagram. The current consumption of this circuit is around 20mA.


Circuit diagram with parts list.