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 circuit was obtained in a 1975 documentation. The maximum frequency depends on the diodes and the...
In the figure we have the basic configuration of an operational amplifier for AC signals using the...
This traditional signal injector from a 1970s publication uses germanium transistors. We can mount it...