This circuit was found in the June 1995 Electroics Now magazine. The relay should be a sensitive type with up to 100 mA trigger current.
This circuit, found in a 1958 magazine, is for reference only, since the components are not easy...
Found in Popular Electronics this circuit triggers an SCR and lights an LED when the location of...
This OF-1 LO oscillator was found in a 1980s American documentation. The transistor can be any...