This is a "Y-Training Cord" that connects two headsets (Plantronics, AddaSound, or VXi - P) to a single phone to perform agent training, supervisory, coaching, multi-users on one call. A mute switch is available on the Supervisor Side. This cord allows only one user to listen/speak while the other user can only listen. To use this cord you will need your 2 Headsets and 1 Telephone Connecting Cord (RJ9 to QD). Note: You will need to have a Telephone Adapter or Telephone Connecting Cord to connect the splitter to your phone. IN THE BOX: The Y-Splitter Adapter is also a mic and headphone splitter, allowing you to use two headsets with one microphone. GTW ""Y"" Splitter/Training Cable for Plantronics Headset The Plantronics Y-Splitter Adapter is a great match for call center and office training. This adapter allows you to connect two headsets to one device, making it ideal for training sessions where multiple people need to be on the same call. It also features a noise-canceling microphone, which ensures that everyone on the call can hear each other clearly. The adapter is also lightweight and easy to use, making it a great choice for any call center or office training.