Plantronics SHS 1890 - PTT (push-to-talk) headset adapter - for Encore H101, H91, StarSet III H31, Supra H51, H61, TriStar H81 Product Type:Headset Amplifier Brand Name:Plantronics Manufacturer:Plantronics, Inc Product Model:SHS1890 Product Name:SHS1890 Headset Amplifer