Headset Buddy PC Headset to 8 Channel RJ9/RJ10/RJ22 Universal Phone Adapter with Mute & Volume Controls (PC35-RJ9x) With 8 channels, you choose the one with best audio clarity. Volume control and mute buttons located on side and top. Use your headset with almost any office phone (Avaya, Cisco, Polycom and etc) - 8 settings cover most phone models Works great with most VOIP phones with a RJ9/Rj10/Rj22 headset jack Convert two 3.5mm plugs to single 4P4C RJ9/RJ10 headset plug Does not work with RJ11 jack, which is wider than your headset jack (6 positions vs. 4). RJ11 jack is what is in the wall. RJ9, RJ10, RJ22 are what is on your phone handset or headset.