Cords and Connectors The increasing variety of cords, ports, jacks and connectors that audio and video engineers are developing can be confusing. Use this guide to identify the cords and connectors you need. If you can't find the answer on this page, just call us at 1-800-450-7686 and one of our friendly reps will help you. RJ9 Connects phones to handsets, headsets and headset amplifiers. 2.5mm Connects headsets to wireless and cellular phones. RJ11 Connects analog telephones to the wall jack. (Note: RJ11 = single-line, RJ14 = 2-line, RJ25 = 3-line) 3.5mm or 1/8 inch Connects headphones and microphones to portable audio equipment. RJ45 Connects most digital phones and computers to networks. 6.35mm/6.4mm or 1/4 inch Connects headphones to guitar amps and mixing equipment. USB Connects digital headsets to computers. RCA Connects wireless headphones to AV receivers and Hi-Fi equipment.