Features: Not Need Battery, power through the Caller display phone wire without additional battery support. Multiple functional telephone that can be used as telephone tester, line maintenance equipment and number checking tool. Simple and easy to use, easily to operate, convenient and quick to diagnose and deal with telephone wire problem. Capable of displaying incomings call number to help users source. Professional who need to detect telephone wire problem quickly and accurately work. Specifications: Component： ABS Size：about 145x45x20mm/5.71x1.77x0.79in Model: D019 Color: Dark Gray Support: DTMF caller information automatic identification and display Support: Last number replays function Support: Date and time display Support: Can be used as regular phone Package Includes: 1 Set D019 Test Telephone Set note: Due to the problem of lighting effect and shooting, there might be tolerances in product, please understand. Please allow 0-1cm error due to the measurment.