The circuit shown is from Texas Instruments optoelectronics documentation. The input signal is audio and equivalent LEDs can be used. Other operational amplifiers can also be used.
In the figure we show how to use a 555 to control an SCR or another type of thyristor. Resistors R1, R2...
This circuit activates one of the selected circuits with a touch of a switch, keeping it...
This powerful FM transmitter was found in 1992 documentation. The circuit requires a 12 V source...