8b/10b

DC balance means that, over some (agreed upon) maximum number of data bits, there are equal number of 1's (positive voltage) and 0's (negative voltage). This is required because the signal that has been encoded needs to be passed either through a capacitor and/or a transformer (both of which will not pass a signal whose average level is anything but zero volts).

Also, the coded bytes (every 8 bits are encoded into a 10 bit word) ensure that there are enough transitions between 0's to 1's (and 1's to 0's) so that a clock can be regenerated at the receiving end.

There should be a ton of stuff on the web. You're not searching hard enough if you haven't found what you need.

Bob

Google search for "8B10B code" and for more than you want, search for "transmission line-code."

Don

Yes, this is what I am looking for. "Troublesome" keywords I have been used.