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. Also includes Caller-ID and Call-waiting Caller-ID functions. 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.