What is in the box:
- Yealink adapter box,
- RJ12 Cord (short round cord)
- RJ45 cord (short flat cord)
- 3.5mm DC Jack Cord,
- RJ9 Curly Cord
- Y-shaped Sennheiser cord (The top of the Y has an RJ9 and and RJ45, bottom of the Y has an RJ45)

Items you need are highlighted above
1) Connect the bottom of the y-cord into the green “phone” port in the cube
2) The top of the y-cord has 2 ends (The RJ45 is shorter than the RJ9 end). Connect the longer RJ9 cord into the headset jack of Yealink phone and connect the RJ45 cord into the left-hand side of the Yealink box
3) Plug the RJ12 cord into the right-hand side of the Yealink box and the other end into the EXT or EHS port on the back of the Yealink phone
4) Set compat to A and move dipswitch #1 down
