This grounding test circuit was found in an American 80's documentation. The circuit is for the 110 V power grid but can be changed to the 220 V power grid.
This overtone oscillator can generate signals up to 150 MHz. The crystal determines the frequency and...
The circuit shown by the figure below can produce signals in the range between 20 kHz and 30 kHz....
This circuit is used to convert audio signals from na amplifier into infrared modulated signals....