Sound and Hear with Remarkable Clarity Yealink Optima HD Voice technology combines cutting-edge hardware and software with wideband technology for maximum acoustic performance. Efficient Deployment and Management Yealink T4U series supports effortless mass deployment and Zero Touch Provisioning with Yealink’s Redirection and Provisioning Service (RPS) and Boot mechanism, making the device management labor-saving and efficient for the administrators. Dual USB Ports for Flexible Expansion Choices Bluetooth/Wi-Fi/Wireless Headset Dongles With the optional USB dongles, the T42U can be enabled of the features including Bluetooth and Wi-Fi or connecting to a compatible wireless headset.