This old circuit from a documentation from the 70s disconnects a TV from a signal obtained on the TV itself, detecting when the tuned channel goes out of the air.
This circuit can operate in a 100 dB range with signals of up to 100 MHz frequencies. Similar...
Suggested by Radio Electronics from the 90s, this circuit is suitable for NiCAd batteries with a...
This circuit is from Delco Radio found in a 1968’s documentation. The transistors are of the time...