Found in Popular Electronics from the 90s, this circuit detects modulated infrared radiation and serves as a test for remote controls. Infrared sensors equivalent to the one indicated can be used.
This circuit appears elsewhere on this site. The CMOS gate can be any one, including NAND and NOR...
In the figure below we have a typical circuit for applying a current sensor that can be used in...
This SCR circuit was found in an American 1980s documentation. The circuit is still current,...