Modular Dual-Prong Plug Headset/Handset-To-Telephone AdapterAdd Plantronics® sound quality and features to operator console, PBX or ADC systems. Easy to install and use, simply plug the adapter into the operator console, then plug in your Plantronics H-series headsets. Durable and portable unit delivers improved sound with a volume equalizer to maintain user listening preferences whatever the quality of incoming calls. Quick Disconnect™ feature lets user walk away from the phone without removing the headset or losing the call. For Use With: Most Telephone Systems.