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.
Found in a 1967 Ferranti documentation, this circuit uses a LDR from that time as a sensor....
This circuit can generate signals from 100 kHz to 1 MHz depending on the L1 coil. For the medium...
This two-transistor circuit was found in the January 1994 issue of Electronics Now. The circuit can...