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.
We found this circuit in Radio Electronics Special Projects from 1992. The circuit turns on the...
We found this circuit in the Texas Instruments' Linear Circuits Applications. It uses an...
This capacitive sensor that operates with a high frequency oscillator was found in Radio...