Voltage level detector (CB21504E)

This circuit was found in a 1966 EEE. The circuit can be implemented with modern general-purpose transistors.

Walkie Talkie for Citizen's Band (CB18701E)
This portable transceiver circuit for the 11 meter or 27 MHz band was found in a 1991...
IGFET Dip Meter (CB5173E)
This circuit was found in an American 1980s documentation. It makes use of an unusual MOSFET today...
Liquid Flow Meter (CB6340E)
This circuit was found in an old Linear Technology documentation. The working principle can be...