Voltcraft CT-20TDR TDR Cable Tester with Length Measurement, Wiremap, Tone Generator for UTP/STP LAN, Coaxial, Telephone Cables

Network technicians and electricians often face the challenge of quickly identifying faults in installed cabling—whether it's a broken wire in a CAT6 run, a short in a coaxial line, or a miswired telephone jack. The Voltcraft CT-20TDR uses Time Domain Reflectometry (TDR) to pinpoint the exact distance to a fault, eliminating guesswork and reducing downtime. This handheld tester combines wiremap verification, length measurement, and tone generation in one rugged unit, making it an essential tool for structured cabling installers, maintenance crews, and IT support staff.

Key specifications

• Measurement technology: TDR (Time Domain Reflectometry) for precise fault location
• Supported cable types: UTP/STP LAN (CAT3, CAT5, CAT5e, CAT6, CAT6a, CAT7), coaxial, and telephone cables
• Test functions: wiremap (open, short, cross, split, reverse, miswire), length measurement, and fault location
• Length measurement range: up to 600 m (2000 ft) with accuracy of ±2% + 0.6 m (2 ft)
• Display: backlit LCD for clear readings in low light
• Connectors: RJ45, BNC, RJ11/RJ12
• Additional features: tone generator for cable tracing and port blink function for switch port identification
• Power: 4x AA 1.5V batteries (not included) with auto power off
• Operating temperature: 0 to 50 °C; storage temperature: -10 to 60 °C
• Includes remote unit for one-person testing

Why choose it

The CT-20TDR stands out with its TDR capability, which not only verifies wiremap but also measures the exact distance to a fault—a feature often missing in basic testers. Its support for a wide range of cable types, including CAT7 and coaxial, makes it versatile for both data and telecom installations. The backlit display and tone generator enhance usability in dark or crowded wiring closets, while the port blink function helps identify switch ports without disconnecting cables.

Ideal use cases

• Certifying new LAN installations in office buildings or data centers
• Troubleshooting intermittent network issues caused by cable damage
• Locating breaks or shorts in long coaxial runs for CCTV or broadband
• Verifying telephone wiring in residential or commercial premises
• Performing preventive maintenance on structured cabling systems

Good to know

The tester measures length in meters or feet, selectable via the menu. The remote unit allows testing of installed cables from one end, saving time on long runs. For best accuracy, ensure the cable under test is not connected to any active equipment. The auto power off function conserves battery life during field use.