Blog
14 Nov 2010
This circuit is a simple intercom circuit based on LM386 low voltage audio amplifier. It uses 8 ohm speakers that works as a microphone and as speaker at the same time. A 10k potentiometer is used to adjust the volume. It also has a double pole double throw switch that is used as push to talk switch.
Simple two way intercom – [Link]
November 14th, 2010 at 5:49 pm
The circuit is missing the very important resistor and capacitor at the output of each LM386 that is shown on [b]every[/b] schematic in its datasheet. The parts prevent high frequency oscillation.
The circuit is also missing a supply bypass capacitor that prevents audio oscillation or motor-boating sounds.
A little speaker has a strong resonance at voice frequencies that causes it to be a poor microphone.