The Fluke Networks 10113000 4-Wire Modular Adapter is a must-have tool for any technician or engineer working with telephone lines. This modular adapter allows you to easily complete testing and obtain circuit access on working lines without disrupting service. The clear circuit markings on the sides and bottom of the unit make it easy to test line status and identify which lines are in use. The modular adapter is available in in line or standard versions and can be used with standard or ruggedized k plug ends.