Low noise amplifier (T466E)

Found in 1948 MIT documentation, this 4-tube amplifier is characterized by its low noise level.

Turn On Switch Using a SCR (CB542E)
This circuit can turn-on (only) a load (relay or lamp) when S1 is pressed. The circuit can be used as...
Biquad filter LM324 (CB4005E)
We found this filter in the 1990 Motorola Linear Databook, but it can be implemented with other...
Whistle control (CB7088E)
This 1969 Philips documentation circuit makes it possible to control an engine through the sound...