HP 200A

The HP 200A Audio Oscillator, first built in 1938, was the first product made by Hewlett-Packard and was manufactured in David Packard's garage in Palo Alto, California. It was a low-distortion audio oscillator used for testing sound equipment, built on the Wien bridge oscillator circuit that had been the subject of Bill Hewlett's master's thesis. It was also the first such commercial oscillator to use a simple light bulb as the temperature-dependent resistor in its feedback network, an inexpensive automatic gain control that kept the output amplitude constant and held the loop gain near unity, a key technique for a low distortion oscillator. The product code was chosen to give the impression that the company was already established. A variation, the HP 200B, was customized for Walt Disney, which bought eight units for the production of Fantasia, and later versions through the 200CD covered a wider range of frequencies and became a common laboratory audio generator from the 1950s to the 1990s.