We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and has 8 digits. Changes can be made using a prescaler to reach higher frequencies.
This circuit interrupts the power supply when grounding is missing. The circuit is from an old...
We found this circuit in an old American documentation. The circuit applies to modern equivalent...
The trigger shown in the figure, built around a 4093 can generate pulses that reach 1 hour with a...