This 1967 Ferranti circuit uses company components. These transistors can be replaced by modern equivalents. The sensor is an LDR.
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...