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 was found in a 90s Radio Electronics. It produces an ultrasonic signal in a special...
This booster for listening to signals in the range from medium waves to 30 MHz was found in a 1998...
The third version for the 4098 is shown here (the others are CIR17E and CIR138E). It is a...