Originally Posted by MichaelW
Gear changing is an analogue information system with 8 states (or recently 9 and 10), rather than the 2 states of a binary system.
The analogue information is transmitted in the form of a certain length of cable which is pulled by the lever. This length is translated into a horizontal throw of the derailleur.
If you use fully shrouded cable, this is increasing noise in the system. The theories of Shannon still hold no matter what type of information we are talking about.
Mavic transmit the gear changing information by electrical cable or infra-red.
http://en.wikipedia.org/wiki/Claude_E._Shannon
Why try and make it rocket science. Index shifting is just precise cable pull.Once it gets to the derailer,that's another story.Certainly the less interference and slop the better. A good reason for downtube shifters.