1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU%.%2!,G0G02%#/-%.$!4)/.3G0G0/.G0G04%,%0(/.%37)4#().G0G0!.$G0G03).!,).).4%2.!4)/.!,G0G0!54/-!4)#G0G0!.$3%-)G13!54/-!4)#G0G07/2+).3934%-3G0G02%#/-%.$%$G0G0Annex B: Carrier systems with 8 channels per group.ANNE
2、X A(to Recommendation Q.21)Out-band signalling systems forcarrier systems with 12 channels per group(The signal levels are quoted in terms of absolute power level at a zero relative level point in dBm0.)A.1 Type I (discontinuous signals)Frequency: virtual carrier (zero frequency).Level: high,for exa
3、mple -3 dBm0.A.2 Type II1) (discontinuous signals)Frequency: 3825 Hz.Level: high,for example - 5 dBm0.2) (semi-continuous signals)Frequency: 3825 HzLevel: low,for example -20 dBm0.A.3 The Type I signalling system is compatible with only those group and supergroup reference pilots having adisplacemen
4、t from the virtual carrier frequency (zero frequency) of 140 Hz.Types II-1 and II-2 are compatible with only those group and supergroup reference pilots having adisplacement from the virtual carrier frequency (zero frequency) of 80 Hz.2 Fascicle VI.1 - Rec. Q.21ANNEX B(to Recommendation Q.21)Out-ban
5、d signalling systems forcarrier systems with 8 channels per groupThe signal levels are quoted in terms of absolute power level (reference 1 mW) at a zero relative level point.Frequency: 4.3 kHz 10 Hz.Level:- discontinuous signals: -6 dBm0;- semi-continuous signals: value between - 20 dBm0 and - 17.4 dBm0.
