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.
This circuit was obtained in a 90s documentation. However, it can be developed with modern...
This circuit uses a 455 kHz crystal or for close frequencies. We found it in documentation from...
This circuit turns off after a time that depends on C1. The circuit is from an Electronics Now...