This circuit was found in the September 1971 Radio Electronics magazine. The buzzer can be replaced by a relay according to the supply voltage. R1 adjusts the sensitivity.
This circuit controls a relay in a bistable way by touching the sensors type NF (CH3) and NO...
This circuit produces modulated tones in a loudspeaker. The effects can be adjusted by the...
This is a simulation of a Relaxation Oscillator using a programmable unijunction transistor (PUT). The...