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 is from the 2005 Linear Technology Application Manual. The circuit must be powered by 5...
Originally recommended to give a tone of transmission in equipment of the 60s (tubed) this circuit is...
September 2017 - Texas Instruments TPS543C20 Step-Down Converters can be found on Mouser...