is no talkdown performance requirement. The near end is always silent and does not interfere with far end modem ANS signals. 6. There shall be fewer than 1 talkoff in 5 hours of call classification when the detector is programmed with the recommended parameters. Assuming that each call is resolved within an average time of 10 seconds, there shall be less than 1 talkoff in 1800 calls. A.5.3.1.8 Three Tone Sequences Most countries that generate Special Information Tones (SIT) use a three tone sequence. SIT sequences are generated by various central offices or common carrier switching points to indicate a problem with the dialed call. A SIT tone sequence generally precedes a recorded voice announcement such as "the number you have dialed is no longer in service..." and is provided specifically for the purpose of detection of the problem type by an automated device. There are two popular types of SIT sequences. The first type is used mainly in Europe. It consists of a sequence of three tones of identical durations. The second type is the one used in North America. There are several North American SIT sequences that are encoded using various combinations of frequency and duration for each of the three tones. The encoding has been standardized by Bellcore. Performance Requirements: 1. The UTD shall handle both types of sequences. 2. There is no talkdown performance requirement. The near end is always silent and does not interfere with far end SIT signals. Software License D2 Technologies, Inc. and Maintenance Agreement August 4, 1997 CONFIDENTIAL 37 3. There shall be fewer than 1 talkoff in 5 hours of voice when the detector is programmed with the recommended parameters. Assuming that each voice call is has an average of 2 seconds of voice, there shall be fewer than 1 talkoff