This is our preferred method for Y-Cabling for use in VDSL Bonding. It is possible to achieve the same result by adding a jack at the “Y” (splitter) point, but this also introduces an extra point of failure that often makes it harder to remote troubleshoot in the future. Instead we create a custom Y-Cable, joining two cables directly into a RJ14 male connector to plug into the DSL Modem. Make sure you are onsite or know the length of cabling required before making these cables.
You will use CAT5 cabling (CAT5 has the required twisted pairs, while reducing noise to increase stability and sync speed) and one RJ14 (6P4C) male connector at the DSL modem end and either RJ11 (4P2C) or RJ14 male connectors for the ends of Line 1 and 2.
This is the wiring diagram for our Y Cable:
A cable tester should be used to verify good connections on all needed pins.
And here is an example of a finished cable: