Grandstream GBX20 LCD Extension Module For GRP2615 & GXV3350 only, 20 Dual-colored Extension Keys, 4.3 inch TFT Color LCDExtension Module GBX20 The GBX20 is an Extension Module that adds functionality, versatility and flexibility to Grandstreams GRP2615 Carrier Grade IP Phone and GXV3350 IP Video Phone. It features a 272x480 LCD display that offers up to 40 contacts per module with support for up to 160 contacts by using 4 modules. The GBX20 supports a wide range of advanced call features including BLF, call park pick up, speed dial, presence, intercom, voice