This circuit was found in a 1967 US documentation. It shows how to build a gain control by digital signals. The circuit can be used as a shield. FET can be a modern equivalent.
This circuit can be used as a shield for microcontrollers such as the Arduino. Frequency is given...
We found this car theft alarm circuit in a 1988 publication, but the components used can still be...
This conventional slow-moving circuit uses incandescent light bulbs, but can be changed to use...