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Reverse Engineering A Two-Wire Intercom

There used to be a time when an intercom used to be merely a couple of bins with audio system joined by way of a few wires, with an audio amplifier someplace within the combine. But intercoms have like the entirety else joined the virtual age, so the ones two wires now lift a load of different capability as virtual signalling. [Aaron Christophel] installs those units for a dwelling, and has posted an enchanting opposite engineering video that we’ve additionally positioned under the smash.

Power for the machine is provide as a relentless 24V DC, and the audio continues to be an old school analogue sign that we’ll all be acquainted with. On that 24V DC although are imposed a chain of pulse trains to cause the other alarms and different purposes, and he describes extracting those with an oscilloscope earlier than appearing us the circuitry he’s used to ship and obtain pulses with an Arduino. The bulk of the video is then dedicated to the device at the Arduino, which you’ll be able to additionally in finding in a GitHub repository.

The end result is an engaging primer for any person who fancies a little bit of serial detective paintings, even though they don’t have a intercom at hand.