This circuit uses a lamp driven by the Hertz loop and measures its brightness with ordinary photovoltaic cells. The circuit is from a Radio Electronics from February 1964.
This circuit with variable capacitance diode (varicap) is from a publication from the 90s. The...
With this circuit it is possible to divide the frequency of a rectangular signal by values between 2...
The presented circuit uses an optocoupler to trigger a triac. We found it in a Popular Electronics from...