parameters corresponds to either a single tone, a dual tone, or an amplitude modulated tone. --------------------------------- Code Tone Type --------------------------------- 0 Single Tone 1 Dual Tone 2 Modulated Tone --------------------------------- Table A-4: Call Progress Tone Types A.5.3 General Functional Requirements UTD functionally combines a single tone detector and a dual/modulated tone detector into a single module. UTD combines the results of these detectors into a single result. UTD has the following requirements. 1. The DSP shall indicate that the first ringback has started after at least 400 ms of ringback like signal has been processed, as long as no other tone type is early detected. If more than one type of tone is early detected, the first ringback reporting shall be delayed until either cadence information disqualifies the other types, or tone precedence is used as a 'tie-breaker'. Software License D2 Technologies, Inc. and Maintenance Agreement August 4, 1997 CONFIDENTIAL 28 2. The DSP shall indicate ringback has stopped when ringback is no longer detected. 3. The DSP shall indicate a busy tone has been detected after the requisite number of make and break intervals have been processed, and no other tone category is still a candidate for detection. 4. The DSP shall indicate a reorder tone has been detected after the requisite number of make and break intervals have been processed, and no other tone category is still a candidate for detection. 5. The DSP shall indicate a number unobtainable tone has been detected after the requisite number of make and break intervals have been processed, and no other tone category is still a candidate for detection. 6. In the event that more than one tone is a candidate for detection, detection is delayed until all characteristics that may disqualify any of the candidates are tested (for example, waiting