Plantronics Vista M22 Headset Amplifier (43596-40)
Wantek Call Center Telephone Headset, RJ11 Headsets with Noise Cancelling Mic for Plantronics M22 MX10 Vista Modular Adapters - AliExpress Consumer Electronics
Amazon.co.jp: Plantronics Vista M22 Headset Amplifier by PLANT : パソコン・周辺機器