A truly decent audio oscillator was only available after 1939, when Hewlett & Packard issued their first instrument. In a 1985 letter, Dave [Packard] described

A truly decent audio oscillator was only available after 1939, when Hewlett & Packard issued their first instrument. In a 1985 letter, Dave [Packard] described Hewlett's audio oscillator as "the foundation on which Hewlett-Packard Company was able to grow into the largest manufacturer of electronic instruments in the world, the keystone that allowed four and one-half decades of major contributions to electronic measurement technology and equipment."