This a two station intercom. It uses two wires to run between each intercom unit. Each is self contained with its own battery, speaker, microphone and amplifier circuit.

An LM386 audio power amplifier is used. It is widely available, used a minimum of external parts and is well suited to battery operation. It will give just over 1W into the 8 ohm speaker. The gain can be varied by the external components attached to pins 1 and 8. Gain can range from 20 (open circuit – pins 1 & 8 not connected) to 200 (pins 1 & 8 short circuited).