Plantronics Avaya APV-66 (formerly APV-65) Electronic hookswitch adapter EHS for use with CS500-Series wireless headset and all Savi Office wireless headset models (WO100, WO200, WO350, W730, W740, etc.), when connected to specific Avaya IP telephone models. This device allows the user to answer and end calls from the headset remotely, while away from the desk by simply pressing the talk button on the earpiece. An audible beep tone is provided in the earpiece to alert the user to an incoming call. The call answer/end function is all electronic (rather than mechanical as it is with the HL10 handset lifter). No lifter is needed! Please feel free to call us if you are unsure which EHS (electronic hookswitch) is right for your Avaya phone. Part #38633-11 APV66 (formerly 38633-01 APV65).