Computer tuning of hybrid audio oscillators

A hybrid tantalum thin-film and beam-lead silicon device will be incorporated in the Bell System's Touch-Tone telephones of the future. This RC multifrequency audio oscillator will replace the LC device presently used in the Touch-Tone keyboards. The tuning process for the RC device requires that the tantalum thin-film resistors be custom adjusted to calculated values; and a tuning system driven by a small process-control computer has been designed to fulfill this function.