Channel Associated Signaling

CAS is known as channel associated signaling. This is the signaling method used in the digital world.

In digital world, we have two type of signaling method one is CAS and another is CCS. In this post, I will be covering CAS T1 which is also known as channel associated signaling T1. CAS signalling is further classify two parts :-
a) T1 CAS Signaling
b) E1 CAS Signaling

T1 is mainly used in Europe, US and other countries. T1 uses 23B+1D channel. CAS in T1 enviornment is always equal to Robbed Bit Signaling (RBS). T1 is having 24 time slots, each timeslot carries 64Kbps and when we club the whole 24 time slots, a single frame is built up.

Frame1:- |Ist DS0|2nd DS0|3rd DS0|4th DS0|5th DS0|6th DS0|7th DS0|.....|24th DS0|F
Frame2:- |Ist DS0|2nd DS0|3rd DS0|4th DS0|5th DS0|6th DS0|7th DS0|.....|24th DS0|F
Frame3:- |Ist DS0|2nd DS0|3rd DS0|4th DS0|5th DS0|6th DS0|7th DS0|.....|24th DS0|F
Frame4:- |Ist DS0|2nd DS0|3rd DS0|4th DS0|5th DS0|6th DS0|7th DS0|.....|24th DS0|F
Frame5:- |Ist DS0|2nd DS0|3rd DS0|4th DS0|5th DS0|6th DS0|7th DS0|.....|24th DS0|F
Frame6:- |Ist DS0|2nd DS0|3rd DS0|4th DS0|5th DS0|6th DS0|7th DS0|.....|24th DS0|F

1010101 0 --> 0 is signaling bit from ist DS0. Same way get the LSB from every DS0.
The least significant bit in every 6th frame is known as signaling. It means every 6th frame will have only 7 bits instead of 8 bits. Thats true. Lets calculate the length of Frame1. 64Kbps * 24 = 1536 Kbps + 8 (Framing Type) = 1544 kbps or 1.544 Mbps.

T1 is having two typed of framing types:-
a) Super frame:- It sends 12 T1 frame at a time. It means 6 and 12th frame will be sent along and we will be having two RBS.
b) Extended super frame:- It sends 24 T1 frame at a time. It means 6,12,18 and 24th frame will be sent along and we will be having four RBS.


regards
shivlu jain

People who read this post also read :