Found in the October 1979 Radio Electronics magazine, the purpose of this circuit is to monitor the coolant level in a car's radiator. The circuit is based on the LM1830.
This simple voltmeter takes advantage of a 150 uA instrument. The circuit is from a Radio...
This circuit was found in an English magazine from 1977. The critical component is the gas sensor....
This commercial receiver manufactured by Sanyo in the 1960s used a loop antenna. The circuit is...