ALL DISCONTINUED! Basic Troubleshoot Features: If you’re experiencing an echo with the 9120 or find that people say they are too soft or too loud, then adjusting the microphone volume will usually correct this. To adjust this volume press and hold the “+” and “–“ buttons on the headset for 2 seconds, then immediately after releasing press either “+” or “–“ depending on if you want to increase or decrease the microphone volume. To mute a call, quickly press the “–“ button twice. Repeat these steps to un-mute the headset. Some common concerns that can occur on the 9120 include: (1) No sound on the headset. (2) One party can hear and the other party cannot. (3) The quality of sound is unsatisfactory. A good starting point to correct these would be to try rotating the dial on the side of the base. The dial toggles from “A” to “G” and on most phone systems works best on either “A” or “G.” The letters are super-tiny, no normal human being can see them. So tell your Customer to scroll all th…