Plantronics M22 Telephone Headset Amplifier and Audio Enhancer with In-Line controls for Mute, Volume, Microphone and Speaker settings - 43596-40
People Can't Hear You On Your Plantronics Wo2 Headset? Here's The Fix – Merrittcomm Blog | Wired & Wireless Headsets, Productivity, Efficiency
Amazon.com: Plantronics Style Headset Splitter and Telephone Cable-Supervisor Agent Training Y-Cord with Mute Button-Compatible w/ Plantronics HW Series headsets, Encore, EncorePro for Call Center, Office Training : Electronics
Blackwire 500 Series: How to Mute a Call | Poly, formerly Plantronics & Polycom