If I am not mistaken, Avaya 1416 is a digital phone. To use this phone on a UCX system, you need the E-MetroTel DSM16 card that converts the Avaya digital signaling to XSTIM. To the UCX system, this phone therefore looks just like any other XSTIM extension. Currently, you can use DSM16 for digital phones from Nortel Norstar/BCM, Nortel M1, Avaya and Panasonic. For a specific list of supported phones, you'd have to take a peek at the E-MetroTel web site.