The UNI-T UT682D is a handheld cable tester and wire tracker designed for network and telecommunication applications. It consists of a transmitter and a receiver, allowing users to trace and identify cables without removing insulation.  
 
Features:

Cable Tracking: Can track Ethernet (LAN), telephone, and power cables.   
Continuity Testing: Checks for open or short circuits in cables.   
Polarity Indication: Tests DC voltage level and polarity on telephone lines (5V-52V).   
Line Sequence Verification: Verifies the wiring order of Ethernet cables.   
Telephone/LAN Distinction: Can differentiate between telephone lines and LAN cables. 
Adjustable Volume: Receiver volume can be adjusted for noisy environments.   
Headphone Jack: For use in loud environments.   
Dual Measurement Cycle Mode: Offers fast and slow testing speeds.   
Low Battery Indication: Alerts the user when batteries are low.   
Signal Strength Indication: LED indicates the strength of the tracking signal.
Transmitter Input Protection: Up to 60V DC.
Long Tracking Distance: Can trace telephone lines up to 3000m.   

It is a useful tool for network technicians and electricians for cable installation, maintenance, and troubleshooting. The UT682D helps in debugging communication and audio/video cables as well.