Grandstream GBX20 LCD Extension Module For GRP2615 And GXV3350DescriptionSpecificationsShipping The GBX20 is an Extension Module that adds functionality, versa tility and flexibility to Grandstreams GRP2615 Carrier Grade IP Phone and GXV3350 IP Video Phone. It f eatures a 272x480 LCD display that offers up to 40 contacts per module with support for up to 160 contact s by using 4 modules. The GBX20 supports a wide range of advanced call features including BLF, call park pick up, speed dial, presence, intercom,