The VDV Mapmaster 3.0 Combines Continuity Testing, Mapping, Generating Tones and Length Measurement Functions Into A Single Easy-to-Use Unit For Installation, Troubleshooting, and Maintenance For Telco, Network, or Coax Cable. The Back-Lit Display, Glow-In-The Dark Keypad and A Built-In Flashlight Helps You to Work In The Dark. Whether Your Jobs Are Commercial or Residential, The Versatility and Added Features Of The VDV Mapmaster 3.0 Makes It A Best Value Cable Verifier For The Professional Installer!