This circuit, found in a 1977 documentation, indicates when the grid voltage goes through zero. Under these conditions, it produces an output pulse whose duration depends on the capacitor.
The circuit shown by the figure below can produce signals in the range between 20 kHz and 30 kHz....
We found this circuit in an article in Electronics Now magazine from November 1997. The circuit uses...
The figure shows how to implement an OR function with two inputs, using a relay. The relay...