CW tone generator (CB21673E)

This telegraphy circuit generates an audio tone from a pure RF carrier. We found it in a publication by Gernsback from 1960.

Metal locator (CB7883E)
Found in a 1966 documentation, this “coin finder” uses components from the era operating at 2.1...
15 V Regulator MA1539 (CB4017E)
This circuit is from a documentation on the MC1539 from Motorola and may, however, be implemented...
Reject filter 747 (CB19907E)
The 747 is an old operational amplifier, but the configuration applies to modern operatives. In...