We found this circuit in an English publication from the 1980s. The circuit uses current components and can be tuned for frequencies between 300 and 1500 Hz.
The purpose of this project is to monitor remote loads. The windings are made in a burnt...
The scale of this scale uses LEDs, and its accuracy depends on the number of LEDs. We found this...
We find this circuit in an American documentation from the 80's. The circuit has the coil given by the...