This circuit from the 90s, found in an Electronic Engineering can be used as a shield since its control is digital with TTL logic of 5 V. The components used are still common today.
The circuit shown in the figure allows a load to be switched on and off (through a relay) at...
We found this simple frequency meter for low frequencies in an English publication from 1978. The...
This circuit has a full scale of 1 kW, being indicated for the 110 V power grid. Adaptations can...