Found in American 90’s documentation, this circuit generates 300 Hz depending on the capacitors used. These components can be changed to obtain other frequencies.
This powerful amplifier was part of commercial sound circuits from the 90s. The integrated circuit...
This circuit generates a control tone that serves to adjust amplifiers, check audio cables. The...
This circuit locks when the sensors are opened. The relay can be 6 or 12 V depending on the power...