Plantronics P51N U10P Supra Noise Canceling Polaris headsets end in a modular plug and are electroniclly configured to enhance performance when used with telephones that have dedicated headset jacks. (The headset jacks are most often labeled) Any confusion please call 800-533-4014. DISCONTINUED Please see replacement models Plantronics H51N and A10 below for superior audio quality | 
