Importance

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Abstract

A call progress monitor for a computer telephone interface system. Energy detectors are connected to receive signals from a telephone line. A bandpass filter is connected to the telephone line, having selectable center frequency. A counter-timer connected to count clock pulses is reset by the energy detector and timing commences in response to the presence of a signal on the telephone line. The counter will result in a center frequency control means for the filter being slewed over a bandwidth of interest, in synchronism with the counting of the timer-counter. A signal detector connected to the filter indicates the presence of a pair of signal tones passing through the filter as it is slewed. Decoding means are connected to the counter-timer and the signal detector for generating a binary signal indicating the frequency of the bandpass filter which passes each signal tone. The binary signal is entered in a data register, and an interrupt posted to a host computer. During the remaining portion of a counting cycle, a cadence interval is detected and the data register is loaded with cadence data. An interrupt is posted at the end of the cadence measuring interval for signalling the computer to read the contents of the data register.

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First Claim