The Aastra 57i hosts a full-duplex speakerphone along with a graphical LCD screen. There is no need to purchase a separate adapter for power over Ethernet (PoE) as a PoE adapter is included with the phone. Aastra 57i IP Phone with Full-Duplex Speakerphone, Graphical LCD Screen & Up to 9 Lines Supported - Connexio 5i Series The Aastra 57i IP Phone has 6 static keys which are programmable up to 10 functions. There is a built-in amplifier along with headset support. The Aastra 57i is expandable up to 3 modules of model 536M and 560M.