This feature-rich test set is a necessity for a variety of installs. The TS25D Test Set 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 analog 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.