Features of Plantronics Headset Amplifiers Question: What are the features on your standard Plantronics headset amplifiers such as the M10, M12 and M22? I’ve misplaced my instructions. Answer: Here are the features. You’re looking at the amplifier in front of you. The single RJ9 jack in front of the amplifier (marked with a headset symbol) should have the coiled “quick … Continued