Metal locator (CB7506E)

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

Transformer coupled AF amplifier (CB21547E)
This circuit is from a book of transistors from 1954. The transistors are from the time and the...
Temperature Test (CB3944E)
This circuit uses a metal enclosed transistor as a temperature sensor. The circuit is from an old...
Multi Frequency Oscillator (CB4226E)
This oscillator for various frequencies was obtained from a 1980s telecom documentation. The...