Cisco 8800 Series Manual page 6

Add Buttons to Your Phone (8800 Series)
Connect a Key Expansion Module to a Cisco IP Phone
Step 7
Connect the other end of the spine connector to the key expansion module as shown in this diagram.
a) Align the spine connector with the key expansion module accessory connector ports.
b) Firmly press the key expansion module into the spine connector.
Add Buttons to Your Phone (8800 Series)
6