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Revision as of 08:20, 15 May 2004 by Tagishsimon (talk | contribs) (Asymmetric Digital Subscriber Line|)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)A back-channel in a telecommunications system typically is a low-speed or less-than-optimal transmission channel opposite to the main channel's direction. The system is asymmetric in that the communication is not the same speed or capacity in both directions - the back-channel being the subservient or lower speed/capacity direction.
In many cases the back-channel is used mostly for acknowlegements of the validity of the forward-channel's data (i.e. that the forward-channel's data passes validity tests of some sort.)
Examples
ADSL where "A" stands for "asymmetric", and the channel from the subsciber to the supplier, is slower and may be of less capacity than the channel from the supplier (ISP) to the subscriber - the channel from the subscriber to the supplier is the back-channel.