This circuit is from Philips' 60s documentation. The circuit can be applied to modern operational amplifiers. The power supply must be 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. ...