Two sensors are used in this simple remote-control circuit, one to switch on and one to switch off the relay. The circuit is from 1986 documentation. The transformer has 12 V of secondary.
This 1992 circuit was originally designed to operate at a frequency around 28 MHz. For this range,...
This circuit uses common diodes as sensors, triggering when the temperature rises by touch,...
This circuit with transistors of the time was found in the November 1972 Radio Electronics...