Disconnect signalling detection arrangement

Year	Description
1993	Invention patented by David J. Marinelli and Kevin M. O'Dell on December 16th, 1993. Abstract: A substantially-universal detector (FIG. 2) of far-end call disconnect-indicative tones detects the foreseeable forms of tone-based signalling of remote-end call disconnect that are likely to be employed anywhere in the world, without reconfiguration or reprogramming for different tones or countries. Implemented in the digital signal processor (DSP 30) of port circuits (14, 20) of switching systems (11) or adjunct processors (12), the detector determines parameters (204) of signals carried by the call to the near end and uses them, along with already-present linear predictive coding (LPC) predictor coefficients (202) and indications of energy (203) in the signals, in a multivariate classification (230) of call progress tones from other tones. When presence of any call progress tones is thus detected substantially without interruption for a predetermined minimum time in the received signals, the call is considered (240) to have been disconnected at the far end. In response, a voice messaging system (VMS) adjunct processor, (12) deletes any recording of the call progress tones from the end of the recorded message.
Source: selected by the editor from original sources.

Invention: Disconnect signalling detection arrangement