Headset Compatibility Notes: Phone has designated headset port. LKA10 & AWH55 plugs into headset port, no lifter required. The AWH55 unit comes with an additional connection cable that goes from the AWH55 EU24 port to EU24 on the bottom of the phone itself to allow remote answer and ring detection. Please note **phone must be above v 4.0** If using the LKA10, there are two scenarios: 1) If the telephone firmware is below v 4.0 the LKA10 will access hook switch control through the headset port, but there is no dial pad functionality. 2) If the telephone firmware is above v 4.0 you can use the MIP adapter with the LKA10 through the headset port to get remote answering, ringing, and dialing.