Thank you... It makes sense, but I still confused because of this: http://www.aculab.com/questions/how-many-voice-channels-does-a-t1-primary-rate-interface-pri-have/Channel 0-22     -           B-Channel (Voice)Channel 23         -           D-Channe...

The question is, why are there 23 channels, where channel 0 should be?... it would make sense if those were TS because of TS 24 is used for signaling.