Originally Posted by
trailflow1
yup, correct.
AFAIK the 'brain' of the system is the junction 'A' box which can also tell you your battery level , and let you fine tune the rear derailleur position (if you hold down the small button,then click the shift levers to adjust.)
The shifters are the control point. They send the signal (the shift) to the motors on the deraillers,which do all the work.
Are you sure? because in this case, the
EW67A-E acts as an "A" junction box with its battery level button and everything, which is why the fact that this item designed for 10-speed Ultergra 6770 works with the 11-speed Ultegra 6870 was far from obvious.
Even though here it seems to be the case which is comforting ...