Grandstream GXP2200EXT Extension Module, 20 Buttons, 40 Contacts, Black//Supported by the GXP2140, GXP2170 and GXV3240128x384 backlit LCD display20 programmable dual-color buttons per module, 2 pages per module (40 contacts total)BLF/speed dialDaisy-chain up to 4 modules for up to 160 contacts/extensionsBLA (bridged line appearance)/SCA (shared call appearance), BLF (busy lamp field, standard or eventlist), Call Park/Pick-up, Speed Dial, Presence, Intercom, and conference/ transfer/forward and morehttps://www.grandstream.com/products/ip-voice-telephony/extension-modules/product/gxp2200ext-expansion-module