This old 4-channel circuit was found in the December 1994 Electronics Now magazine. The circuit uses a 556 as a modulator. Note the code programming key.
This circuit can use both separate LEDs and a common cathode display when one segment indicates...
The first transformer is a driver found on transistor radios and the second a small output...
Signals of up to a few tens of kilohertz can be generated by this circuit found in a European...