This new feature-rich test set is a necessity for a variety of installs. The TS25D features data lockout and lockout override, making you completely safe in talk or monitor mode. The DSL/POTS filtering technology allows you to safely draw dial tone without downing DSL. A built-in tone generator simplifies wire identification with a probe. An amplified speaker makes monitoring the line hands-free, so you can keep working. The Talk Battery function provides voltage to carry voice conversation on non-powered pairs. All in a compact unit with an oversized robust liquid crystal display (LCD) that makes the intuitive, common-sense menus easy to read and use.This test set is so user friendly you will think you are using your cell phone. The unit operates on a 9V battery (included) and allows programmed timeouts to further prolong the life of the battery. The unit measures 7.8 x 2.7 x 1.6", weighs 10oz and ships with an angled bed-of-nails cordset.