Found in an Electronic Design and 1970s, this circuit uses transistors of the time. The transistors can be replaced with equivalents and the relay is 12 V depending on the power supply.
Texas Instruments' low power operational amplifiers OPAx196 can be found on Mouser Electronics....
This circuit operates with input voltages from 50 to 140 V providing an output of 12 V under...
This circuit mimics the sound of a siren when we turn the axis of the small DC motor. The...