Time-domain reflectometer
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In telecommunication, a time-domain reflectometer (TDR) is an electronic instrument used to characterize and locate faults in metallic cables (e.g., twisted pair, coax).
It is indispensable for preventive maintenance of telecommunication lines, as it can reveal growing resistance on joints and connectors as they corrode, and decreasing parameters of insulation as it degrades and soaks moisture, together with the approximate locations of the potential faults, long before they lead to catastrophic failures.
TDR is also a very important tool for TSCM, where it helps locating wiretaps.
Note 1: A TDR transmits a fast rise time pulse along the conductor. The resulting reflected pulse is measured at the input as a function of time and displayed on the instrument or plotted, as a function of cable length. This is principially similar to a radar.
Note 2: A TDR may be used to verify cable impedance characteristics, splice and connector location and associated losses, and estimate cable lengths, as every nonhomogenity in the impedance of the cable will reflect some signal back.
See also
- Optical time domain reflectometer
- Federal Standard 1037C
- Riser Bond Extended Training (http://www.riserbond.com/Ext/Extmenu.html) - ABC's of TDR's