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.
With the change of the coil, the circuit can operate at frequencies between 30 MHz and 150 MHz....
The frequency of this Pierce oscillator, found in 1969 documentation, depends on the crystal. The...
This simple circuit can be used to power a simple communication system using ordinary telephones....