Using an LDR, this Philips circuit directly activates a relay when light strikes the sensor. The relay is 45 V with 20k coil resistance. The 220 nF capacitor must be polyester for 400 V.
This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit...
In the figure we have the way to implement a sinusoidal oscillator with the 4093 IC. The component...
Equivalent transistors, like the BC548 and BC558 pair can be used in this circuit that we find in an...