In general terms, a CIC is a channel within a route.
Whereas a 2Mb has 31 usable channels, and each is identifiable by the timeslot, a route may contain multiple 2Mb’s, and a method is needed to identify the 2Mb and timeslot. This is where a CIC is used.
So if you have 2 2Mb, and keeping it simple, just 30 usable timeslots per 2Mb, CICs 1 to 30 would be in the first 2Mb, and CIC’s 31 to 60 would be in the second 2Mb.
regards, AndyT