The Grandstream GBX20-EXT is a backlit LCD extension module. The module includes 20 dual-coloured extension keys and 2 arrow keys for page switching (allowing each GBX20 to support up to 40 contacts/extensions.).
- Connect up to 4 GBX20 modules to compatible Grandstream phones for a total of 160 contacts/extensions.
- Compatible with: GRP2615, GRP2624 and GXV3350.