+/-15%. c) The power of a CNG tone is between 0 and -43 dBm. Performance Requirements: 1. The detector does not miss any CNG signals on a prerecorded tape containing 50 CNG tone samples collected from S different FAX machines. 2. The detector does not miss any CNG signals from the same FAX machines connected to a local CO with a noise level of less than -45 dBm. 3. The detector misses less than 0.5% of CNG signals (generated at -10 dBm) when compressed voice is output at a level of-15 dBm or less (average over 3 seconds) into a network whose ERL is greater than 15 dB. 4. The detector does not falsely detect more than 1 CNG tone per 5 hours of voice (based on Bellcore recorded talk radio voice tapes.) A.5.3.1.7 Modem Tone Specification All answering modems that conform to the ITU V.25 answering sequence present a 2100 Hz tone 1.8 to 2.5 seconds after answering the telephone line. Figure A-6 and Figure A-7 show the timing of the answering tone (ANS). In Figure A-6, the 2100 Hz Software License D2 Technologies, Inc. and Maintenance Agreement August 4, 1997 CONFIDENTIAL 35 tone reverses phase every [tau] intervals. These phase reversals disconnect echo cancellers and echo suppressors from the network. According to ITU G.164, phase reversal shall be accomplished such that the phase is within 180 +/-10 degrees in 1 ms and that the amplitude of the 2100 Hz tone is not more than 3 dB below its steady state value for more than 400 musec. INSERT GRAPH Figure A-6: Timing for Answering Modem with Phase Reversal A timing diagram for an answering modem without phase reversal is shown in Figure A- 7. The timing is identical with that of phase reversing tone except for the reversal timing.