7" 800 x 480-pixel color touch screen with backlight Yealink Optima HD Voice Up to 16 SIP accounts 29 one-touch DSS keys 7 fixed feature keys - message, headset, hold, mute, transfer, redial, hands-free speakerphone LED for call and message waiting 4-way navigation cluster with 6 navigation keys 4 context sensitive soft keys Volume control Dual-port Gigabit Ethernet Powered via Power over Ethernet or optional AC adapter (not included, sold separately) Headset support (RJ9) Built-in a USB port for Bluetooth headset support (via optional BT40 Bluetooth dongle; sold separately) Supports up to 6 expansion modules for attendant console applications Wall mountable Simple, flexible and secure provisioning options USB 2.0 port for future Bluetooth, WiFi, and USB recording feature expansion T4S series features unified Auto-P template and unified firmware that provides simplified management and maintenance Opus codec support - 8kHz (narrowband) and 16 kHz (wideband) sampling rate Compatibility Can be used with a variety of SIP compatible hosted service providers and SIP compatible IP PBX systems Check with your hosted provider or IP PBX documentation to confirm system compatibility