This circuit was found in a 1967 General Electric documentation. Tunnel diodes can oscillate at very high frequencies. These are not currently easy to obtain components.
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...