This 1977 circuit only allows the solenoid to energize if the right combination of switch positions is selected. The relay is 6 or 12 V depending on the low voltage supply used.
We found this symmetrical regulator in a documentation from the 70s. The circuit uses components...
This circuit was found in a 1995 documentation. It drives a set of sequential LEDs from the sound...
This sophisticated remote field strength meter circuit was found in a 73 magazine for radio...