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.
This oscillator can use inverters or connected AND or NAND gates as such. The signal produced with...
This project, found in a 1981 documentation, consists of an interesting adaptation of the test...
This 1970 circuit triggers a load when it receives a signal. Components are common and SCR admits...