Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
This encrypted key was found in a 1989 documentation. It controls a relay that is activated only...
This circuit is from an American transistor book from the 60's. The transistor is germanium of the...
This simple SCR alarm circuit was found in an old Poptronics, but can be easily assembled as all...