I have an Avaya Telephone, S/N071623004184 with the additional numbers 700381585 2420D01B - 2001 HAC listed on the same sticker as the Serial Number. What Model is this phone? Where can I see a picutre along with the manual for this phone? I'm trying to learn how it works, as well as, find what headset (Plantronics) works with this set. Your assistance would be greatly appreciated! I may be emailed at ghalbert@carilion.com or galbert3@verizon.net.