The Panasonic KX-NT553-B is an IP Proprietary Telephone designed for use with compatible Panasonic PBX systems, including the KX-NS1000, KX-NCP500, KX-NCP1000, KX-TDE100, KX-TDE200, and KX-TDE600. It is not a standalone phone and requires an operational Panasonic PBX to function. The phone features a 3-line graphic backlit LCD display (242 x 55 pixels, 24 characters per line, 4 contrast levels) with 12 self-labeling flexible CO buttons organized across 2 pages, providing 24 total programmable keys. Four soft keys and a full navigator key set allow quick access to call features and system menus. The wideband-compliant handset is Hearing Aid Compatible (HAC, TIA-1083) and supports G.722, G.711, and G.729A audio codecs. A built-in full-duplex speakerphone with 8 volume levels enables clear hands-free communication. Two Gigabit Ethernet ports (10/100/1000Mbps) connect the phone to the network and pass traffic through to a desktop PC from a single wall port. The phone is powered via PoE Class 3, so no AC adapter is required. The 3.5mm EHS port supports selected Plantronics-brand wireless headsets for remote call control, and a 2.5mm jack accommodates standard wired headsets. Up to 4 KX-NT505 48-key DSS add-on modules can be connected (1 maximum when wall-mounted). Wall-mount kit KX-A433 and AC adapter KX-A239 are available as optional accessories.