This circuit activates a relay when the supply voltage drops below the value set in the trimpot. The transistors can be the BC548 and BC558 and the 6 V relay. The circuit was found in a 1999 Poptronics.
This 5-transistor receiver was obtained from an article in the February 1969 Radio Electronics magazine....
The oscillation of the relay causes the applied audio signal to deform and start to resemble the...
Using period transistors, this 10 W amplifier was found in Radio Electronics magazine from May...