The SIP-T42U IP phone is a feature-rich business tool for excellent communications and extended functionality. Integrated with Hall Switch, T42U gives you a quieter operation and environment. Coming with plentiful built-in programmable keys, this 12-line IP phone guarantees the enhanced productivity. United Yealink Optima HD Voice technology, the T42U awards you the superb audio quality and crystal-clear voice communications. The phone feels quicker and more responsive when performing call features. Moreover, the T42U puts dual USB ports in a phone that makes Bluetooth, Wi-Fi, USB headset and USB recording come true, and you can use any two of them freely according to your needs. The Yealink new T4U series offers the same elegant appearance as the T4 line, but with improvements for greater interoperability and better collaboration. The T4U series better builds the Yealink ecosystem and is compatible with more Yealink headsets, supporting intelligent channel switching* and using the phone to configure and upgrade headset.