With this circuit any number of 4017 integrated circuits can be connected in series. The circuit is from a Radio Electronics from April 1989.
This circuit was found in documentation from the 1980s requiring a variable power supply from 0 to...
This photo-relay uses a Darlington stage to increase sensivity. Any photo-transistor can be used....
This is the receiver circuit for the CB13978B, found in the same 1977 Elettronica Prática...