Modem inline modular adapter, 4-conductor to 4-2-conductor, designed to allow modem access to center pair while still allow a phone access to the same pair, labeled: PHONE and MODEM. 1 x RJ14 Plut Input. Phone: 1xRJ14 Jack Output and Modem: 1xRJ11 Jack Output. 4 and 2 conductor modular T adapter that is ideal for combining voice and data transmission through a single jack. U.L. Certified