In my previous post, I have talked about CAS T1 in this post, I will be covering CAS E1. CAS T1 is no more used by service providers. CAS E1 uses 32 channels from DS0 to DS31 but the signalling and framing is carried by different frames. Channel 0 is used for framing and channel 16 is used for signaling. It means channel 1-15 and 17-31 are used for data.
Frame 16 is having 8 bits. First 4 bits are used for 1 to 15 and rest 4 bits are used for 17-31.