Sennheiser Universal Wideband Interface Phone Amplifier Model UI770

Sennheiser UI 770 interface unit + accessories. Great condition. My husband takes such good care of his electronics, but he's purchased a new phone for the office and wants to sell this. Includes: - Headphone connector - Phone cord to connect amplifier to phone - PC USB cord to connect amplifier to PC (this is an extra add-on) - Requires one (1) C battery (there's one already in it) - Compatible with two other items I also have for sale: (1) the Yealink IP phone, and (2) Sennheiser headset