Simple Two Way Communication Intercom Circuit Schematic diagram

Intercom or Inter communication circuit is a two directional communication system. It provides a reliable communication line and is extremely easy to implement. The circuit is prepared by an amplifier, two switches and two loudspeakers. We can extend this circuit by adding more number of speakers with the help of switches. IC LM384 works as a power output amplifier in this intercom circuit. LM384 provides almost 2 watts of audio power via 15 volts supply voltage. This intercom circuit diagram is very simple and practical circuit capable of using intercoms for homes, office intercom.

Circuit Diagram of intercom systems

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Components required for two way intercom

Power supply (15V)
Resistors (1kΩ x 2; 5.6kΩ; 22kΩ; 100Ω x 2)
Preset (10kΩ)
Capacitors (0.01µF; 0.1µF x 2; 0.047µF, 220pF)
Electrolytic Capacitors (10µF:25V; 100µF:25V x 3; 47µF:25V x 2)
Transformer (220/6V step-down)
NE5534
LM384
Speaker/ Microphone (8Ω)
2 Way Switch x 2

Working of wired intercom

Here the 8Ω speaker acts as Microphone as well as Speaker according to the switch positions.

If switch S1 is in ‘Talk’ contact, L1 functions as a Microphone. If it is in ‘Listen’ position, L1 functions as a Speaker. (Similar case applicable in L2 also.)

Time being let’s consider S1 is in ‘Talk’ position and S2 in ‘Listen’ position.

Since the majority speakers are available with impedance low, an impedance converter is required to retain a high-quality audio.

Impedance matching is done by the transformer T1. (This transformer is an ordinary 220/6V step-down transformer.)

IC NE5534 works as a Pre Amplifier which boosts the Audio signal before applying to the LM384 amplifier section. The gain of the LM384 op amp amplifier is set to 11.

The output volume can be adjusted by varying the R4 preset.

In order to use this circuit as intercom, the band width is chosen to 160 Hz to 10 kHz. Selection of other band width range results a HIFI amplifier.

Place the power supply unit independently from the main circuit to avoid interference.

By changing the switch positions of S2 in to ‘Talk’ position and S1 to ‘Listen’ position, L2 get connected to the input section and L1 connected to output section.

Then L2 functions as Microphone and L1 as Speaker. Thus 2 directional communications is achieved…!

Circuit easily used for house intercom or home intercom systems.