Yealink Model #s EHS 40 is compatible with : SIP VP59, T58A, T57W, T53W, T54W, T53, T48S, T46S, T42S, T41S PLEASE NOTE : If an expansion module has been connected to the SIP- T58A, T57W, T54W, T53W, or T43 IP phone, you can connect the EHS40 to the expansion module Plantronics : Grab the adapter box, and the Plantronics Y-cord 1) Connect the bottom of the y-cord into the back of the CS500 headset base 2)Connect RJ45 and RJ9 end of the y-cord into the 2 available slots in the Yealink adapter box 3)Plug the USB cord coming out of the adapter box into the USB port in the phone 4)Compat on A Does not immediately give ring detection. To get it to work correctly, they will need to get to the web portal and do the following : Please go to phone web portal > Features > Audio > Ringer Device for Headset, then choose Use Headset & Speaker. The below picture for your reference.