We found this circuit in a 1968 Electronics World. The transistors are from the era and information about the transformer was included. Transistors support current equivalents.
When the sensor, an ordinary photo-transistor, receives light, the relay closes its contacts. The...
This circuit consists of a bass filter that can be used as a subwoofer in a sound system. The...
This circuit has a traditional configuration often found on this site. The transistor must be...