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 found in an English magazine from 1973. The magazine no longer exists, but the...
This radio version of 1 transistor, extensively explored on this site and in this section, is from...
This dual control was based on Texas Instruments documentation for the CD4050. The circuit has two...