Metal locator (CB7506E)

This simple metal detector was found in a 1960 Sylvania transistor manual. The phone must be high impedance or crystal.

Negative Regulator Power Supply (CB13065E)
In the same way that we can regulate the voltage in the positive branch of the circuit, we can...
Visible optical link for RS232 (CB21602E)
Based on the MC1488 or MC1489 operational amplifiers, this circuit has a 5000V isolation driving a...
3-Transistor Radio (CB21641E)
Found in the July 1968 Supertena Bulletin of a Popular Electronics, this receiver makes use of the...