Hi Rajesh
I like this forum very much basically i am SWITCH engg but i have worked on R2 systems as from my previous knowledge and basic concepts i can say that every time slot get its chance after every 2ms that is very simple to calculate as to complete all the time slot for one E1 32 time slot we require 16 successive frame that is called multiframe and each frame is of timming 125 micro seconds each leads to 2 ms(125micro sec*16).That’s wht CAS is also called slow signaling
As per your question it will be more clear if i could find how many bits will be required to trancefer one single digit as every time slot gets only 4 bits to be send every 2ms.
But i am sure it may help u to understand the concept