We found this circuit in an old American publication from the 1980s. Transistors can be general-purpose types like the BC548, and the tuning frequency is given by the L and C components.
The relay of this circuit closes when the position set in P2 is reached by the sensor...
This circuit is intended to monitor the flame of gas heating systems that must always have a small...
This circuit makes use of an old operational one to generate clock signals that depend on the...