MODULAR-3 WAY-IN-LINE-ADAPTER Connects 2 devices to existing phone cord with connector. Instructions: 1. Plug the 3-Way In-line Coupler to a phone cord 2. Plug any 2 telecom devices into the jack Note: most homes are wired for 1 or 2 line service. For 3 lines, the home or office must be wired with 6 conductor or 8 conductor for 4 lines.