Audio Oscillator 200B

Hewlett-Packard's first product, 200A has a range of 20 Hz to 20 kHz and 200B can distribute 35 Hz to 35 kHz. General Radio before was the leader for RC-audio generators and other bench instruments. The incandescent lamp of 110 Volts and 3 Watts in the cathode path stabilized the result very efficient in a way that HP soon became a leader for this type of instrument.

Info on HPs page:
See also Bill Hewlett's prototype resistance-capacity oscillator from 1938 and the 200A audio oscillator.
In 1938, when the sound engineer for the movie Fantasia from the Walt Disney Studios saw the Model 200A audio oscillator in action, he asked Bill Hewlett to make some modifications to it, and the Model 200B was born. Disney ordered eight of the Model 200B at $71.50 each.

The Model 200A began as the subject of Bill Hewlett's master's thesis at Stanford University in the late 1930s. Bill had the innovative, elegant and practical idea of using a light bulb in a Wien bridge oscillator circuit to solve the problem of how to regulate the output of the circuit without causing distortion. Other oscillators that were available at that time were costly and unstable. By the clever use of the light bulb, Bill was able to simplify the circuit, improve the oscillator's performance and reduce the price.

Some 200B were produced for the Naval Research Laboratories during World War II.

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