Dual tone control with the 6C5 (T1074E)

This circuit was found in a Radio Craft article from 1946. It can be implemented in any amplifier by taking power to the tube from it.

100 kHz Calibrator (CB5607E)
This circuit was obtained from Popular Electronics of the 1990s. The circuit uses common...
50 Ohm Line Drive Amplifier (CB4040E)
The circuit shown uses an operational transconductance amplifier such as the LM3900. Transistors...
Code Practice TTL Oscillator (CB4188E)
This simple Morse Code oscillator was found in a 1980s American documentation. The power supply...