4 Wire (2 pair) cord coupler.In-Line Phone Coupler Ivory RJ11 4 Conductor Female to Female Cord Extension Plug Connection Line Connector Cable Telephone Snap-In, Standard Splice Jack Add-On Allows two phone cords to be connected. Fits all standard modular phones. Instructions: Snap modular plug from phone into one end of modular coupler. Insert modular plug from wall into opposite side of coupler. To remove either modular plug, depress clip and pull. Important: can not be used between phone base and Handset Receiver.