Found on a 1969 EDN this circuit switches a current from a digital control signal. The impedance of the circuit ON is approximately 10 ohms. Modern equivalent transistors may be used.
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...