Short Wave Converter (T987E)

The conversion range of this circuit depends on the coil. The circuit uses two tubes, and the power supply is not provided.

Precision Current Drain (CB14077E)
This circuit is from the 1994 Linear Applications Handbook. The operational circuit can be...
Adjustable Current Regulator (CB17583E)
This circuit is suggested by National Semiconductor (now Texas) in an old manual. The circuit...
Phone circuit (CB8709E)
With this circuit, found in a 80s Popular Electronics, it is possible to use two ordinary phones in a...