Yealink T48s - Phone Installation Guide; Attaching Stand or Wall Mount

Guided Setup
Attach Stand
Attach the stand as shown below.
BBB
40
AAA
45
Connect Handset and Optional Headset
Note: Your phone supports wired headsets, including electronic hookswitch (EHS) headsets.
For connection directions, refer to your headset documentation.
EHS
PC Internet
2