Clear Channel on a T1

Can anybody give me some info on what exactly "Clear Channel" means in
relation to a DS1 circut?

My gut tells me that it's only relevant with voice Ts...

-carl hirsch
network analyst
sargent & lundy llc

Clear channel allows the use of the full 64Kbps per time-slot, or
1.536Mbps aggregate data for the entire T-1; through the use of B8ZS line
coding. A Non-clear channel T-1 only allows use of 56Kbps per time-slot, or
1.344Mbps aggregate data; when using AMI/ZCS line coding.

I came across this, figured I'd post rather than just reply privately,
since others might be curious: