This shield circuit with an optical coupler was found in an 90s EDN. The circuit can be used with voltages from 0 to 600 V with the indicated component values.
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...