Found in a Popular Electronics from the 90's, this circuit detects the approach of objects by the reflection of the radiation emitted by the LED. The relay is a 12 V sensitive type.
ON Semiconductor CMOS Operational Amplifiers Mouser Electronics announces the availability of ON...
Found in Ferranti's 1969 documentation, this circuit can be mounted with a modern equivalent...
This configuration is from a 1964 US documentation valid for any FET. The range of power voltages...