Frame/Handlebar Junction

EW-RS910

The EW-RS910 junction box replaces the more traditional below the stem junction SM-EW90. It is mounted either in the handlebar end or somewhere built into the frame.

The junction box has two E-tube ports to connect it to the rest of the system, a charging port and a button used to check battery status and change settings on the fly.

You could replace this junction with the mountain bike System Information Display (XT SC-M800 | XTR SC-M9051), if you wanted to. This Information Display functions as a Junction A with three e-Tube ports, a display and features Bluetooth/ANT+ connectivity.

Of course the older SM-EW90 junction would be a decent alternative too.

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Installation help

Installing this junction is a little less straight forward than you'd expect, but it's not hard. I've written an EW-RS910 bar-end Junction installation guide that should help you install this junction. Of course, feel free to send a message if you have any questions.

What does the button do?

Depending on the battery and other components installed on your bike the junction box button behaviour changes. As described in the Di2 Beginner's guide, pressing the button for 0.5 seconds will turn the LED red and enter adjustment mode, allowing you to index the rear derailleur or adjust the front derailleur top limit.

You can trigger rear derailleur crash protection reset mode by presssing-and-holding the button for 3 seconds, until the red LED starts to flash. Make sure you turn the cranks, because the rear derailleur will then go through all the gears.

If you have the BT-DN110 battery or BM-DN100 external battery mount though, the button behaviour is:

Press-and-hold the button for 0.5 seconds to enter Bluetooth LE connection mode (red and green LEDs will flash)
Press-and-hold the button for 2 seconds or more to enter adjustment mode
Press-and-hold the button for 5 seconds or more to trigger rear derailleur crash protection reset

Note that if you have a modern battery you'll probably also have a synchronized shift capable bike and pressing the button twice will let you change the current shift mode.

The LEDs

Besides the button, the junction also has two LEDs. Besides indicating whether the bike is in adjustment mode, Bluetooth pairing mode or triggering rear derailleur crash reset, they can also indicate the battery charge level and selected shift mode