Audio Frequency Counter (CB21917E)

This circuit was found in the Raytheon transistors manual from the 1960s. The circuit uses germanium transistors, and the instrument is analog type.

Delay with UJT and SCR (CB21419E)
This circuit was taken from the 1967 General Electric SCR Manual. The circuit can use virtually any...
Speed control using tachometer (CB7157E)
Found in National Semiconductor documentation from the 1980s, this circuit employs a power...
9 V x 200 mA power supply (CB1159E)
The different aspect of this source is the use of a 12 V lamp as a current regulator together with a...