To successfully use your headset with your NEC phone you will need to perform two tasks; 1) Enable the Headset Mode on your NEC phone and 2) Adjust the settings on the smart cord to #7. The video below will demonstrate how to adjust the settings on the smart cord.
If you have questions about your NEC phone compatibility and which accessory is required for your phone feel free to start a chat session or call us 703-766-6363. Global Teck Worldwide provides a ProSetup Service ($35) that walks you through the complete installation of any headset on our website.