Using old germanium transistors like the CK722, this circuit has good gain. We found it in a publication from the 50s.
This circuit was obtained in a 1977 magazine, but it can still be easily assembled, as the...
This intercom for the 27 MHz band was found in a recent English documentation, working with a...
This relay shield circuit for old computers was found in January 1983 Radio Electronics magazine. The...