Two-Tone Audio Generator (T326E)

This 1965 circuit generates 250 to 2,000 Hz tones with quality sine waveform. The power supply is not given and the tubes are of well known types.

MOSFETs SuperFET III (COM034E)
It can be obtained from Mouser Electronics new superFETs III from Fairchild for voltages of 700 V...
Water Level Control (CB5314E)
This water level control circuit was found in a 1980s documentation. The circuit uses a capacity...
Balanced Modulator (CB4224E)
This circuit was found in a 1980s telecommunications publication. The circuit uses a diode bridge to...