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. Color-screen Expansion Module EXP43 The 4.3-inch color screen expansion module is designed to offer advanced call handling capabilities with its simplified UI and up to 60 programmable keys for various features.