The article presented below describes a very simple intercom system which can be built and installed at any required place very cheaply. The circuit utilizes just a single IC and a very few other components for the entire assembly.
How it Works
If you are looking for a simple and low cost intercom system for home installation, you would love the explained project.
The circuit only uses a single chip for the amplification purpose and a couple of speakers along with a handful of passive components for acquiring the intending intercom application circuit.
As seen in the figure the entire circuit hovers around the IC LM380 which is another versatile amplifier IC just like it's younger brother IC LM386.
The IC is manufactured by:
However this chip is even better as it requires very few external components for implementing the amplifier actions.
In the diagram we see that the input of the IC is connected to a small loudspeaker via a small output transformer.
The output of the IC is also connected to a loudspeaker.
A DPDT switch is configured and connected to the two speakers such that the whole circuit works like a two way intercom system.
The connected loudspeakers act as a speech producing devices as well as mics for capturing sound signals for amplification to the other end.
The right end speaker is the master while the speaker connected at the other end is for remote installation.
When the switch is positioned toward the talk mode, the master speaker behaves as the mic, and the sound signal is announced and heard over the remote speaker.
When the switch is positioned toward the listen mode, all the conservation that might take place around the remote speaker is transferred and can be heard over the master speaker.
T1 is nothing but a small audio output transformer which may be easily procured from the market, the winding with lower impedance goes to the speaker while the side with the higher impedance gets connected to the input of the IC.
Circuit Diagram
Simple Intercom using Transistors
A simple intercom can be also built using just a couple of transistors as shown below:
For complete explanation you can refer to this article
I very much commend you for the strength you built up to be producing all these cct. diagrammed.
(1) I have confusion on how to connect S1 and S2 in a PCB, please fix the two switches physical on the PCB and explain the type of switches they are.
(2) what type of transformers T1and T2 are.
(3) connect the remote terminal in the circuit, I do not understand the symbolic way they are now.
Thank you.
Hi, thanks, I would recommend you to build the first circuit, which looks much cleaner and easier to configure. For the amplifier you can simply replace the LM380 with Lm386 amplifier module.
The switch is a DPDT type switch.
The transformer can be any small audio output transformer.
The use of transformers, because of the difficolty to find it easily, greatly reduce the willing to consider the project
You can replace the transformer with any suitable BJT preamplifier circuit.
Have you got a simple circuit for using a couple of those basic speaker mics that the 2-way radios use? They’re available pretty cheap, and contain both a speaker and a mic. The push-to-talk switch could be used to turn on the amp?
Thanks!
John C
I guess you are referring to walkie-talkie circuits, here’s the link where you can find a few of those circuits:
https://www.homemade-circuits.com/?s=walkie+talkie
How do i get operation intercom with speaker and this circuit is used tda2003?
replace the LM380 stage with TDA2030 stage
wish I could communicate with some nearby buildings wireless, could you help?
you can do it by using two FM radios and two small FM transitters, tune these at slightly different stations for communicating across them.
what is the switch used in the listen and talk? does this have a mic?
the speaker works both ways, as a loudspeaker as well as a mic