Yealink T48G-SKYPE FOR BUSINESS EDITION User Manual page 233

If you connect two expansion modules, connect the Ext out jack of the previous expansion
module and the Ext in jack of the second expansion module using another supplied cord.
Note
Up to six expansion modules can be connected to the T48G Skype for Business phone. If you use
more than two expansion modules on a single phone, you need to connect an additional power
adapter to any one of the expansion modules.
To attach the stand of the expansion module:
Wall mount method (Optional)
a)
Desk mount method
b)
EXP40 Expansion Module
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