We found this circuit in a Popular Electronics from the 80s. This circuit eventually doesn't work with modern, higher speed controls. Experiments must be done.
Found in an 80's Elektor, this circuit can use any equivalent optical coupler. The buzzer is of the...
This circuit is suitable for use in radio receivers to improve the quality of weak signal...
Using an LDR as a sensor, this circuit from a 90s Hands-On Electronics triggers a relay in the...