Found in Radio Electronics from the 90's, this circuit can be implemented with other operational amplifiers. The power supply is symmetrical.
This 1960s Signalite circuit uses two SCRs to achieve full wave control. The trigger elements are...
This shoot-to-target game uses well-known CMOS circuits and the player hits the LED by squeezing...
This TTL circuit can be used as a shield. The frequency can be changed by changing the capacitors. ...