Grandstream GXP2200EXT Expansion Module connects to a Grandstream GXP2140, GXP2170, or GXV3240 phone, adding 20 dual-color programable buttons. Power users and executives will love the greatly increased functionality and the simple controls. The module has two arrow keys to switch between pages, meaning each button actually supports 40 contacts or extensions. You can daisy chain up to four GXP2200EXT attendant consoles to the main unit, giving you up to 160 additional line appearances and speed dial contacts. The expansion modules are powered through the main phone.