TDR trace
Wiring bundleGetting To the heart of your telephone or broadband physical line fault or more to the point the actual cause of service performance issues. Line faults are often not clearly visible to the naked eye, irrespective of routing (buried underground, pole span, attached to a property).  There is in fact a simple way to identify both the type of fault & a relatively accurate distance to the fault itself.


The technique is called Time Domain Reflectometry, simply put it is a method of measuring a known quantifiable electrical signal as it travels along a cable. This technique has been around for quite some time & has been widely used by the likes of BT Openreach to help maintain the cables on its network.


TDRAs the cost of this type of testing equipment comes down & the availability goes up it becomes a simple matter of technical training to fully understand how TDR's can be really effective in helping to quickly resolve communication line faults. Additionally this type of test equipment has become much more user friendly & easier to use. Rather than having to understand the output of a signal trace on a time relative graph it is possible to buy TDR units that offer simple test routines, with results output using simple technical terminology.


In the early years a technician would have to undergo comprehensive training to fully understand the principles behind deciphering graphs like the ones shown below.


High resistance joint

tdr high resistance joint





Lateral also some times referred to as a Bridge Tap

tdr lateral bridge tap





Open circuit

tdr open circuit





Short circuit

tdr short circuit





The cost of portable TDR technology has come down significantly.  As such faults on your supply network are relatively easy to find, however the cost implications of quickly rectifying all of them often present some commercial viability issues. However if you need to locate a fault on a communications cable owned by yourself, your small business or commercial site then Burytec are able & happy to help your through the whole process. TDR testing works on both internal & external cable & can help identify exactly how much of a cable needs to be replaced.

A TDR can help diagnose many more types of line conditions than show in the traces above, so if you want to get more technical & understand some of the additional features TDR technology has to offer, a good start would be to do some online searching for the following terms:-


  • Pulse
  • Impedance miss match
  • Velocity of Propagation
  • Spread Spectrum Time Domain Reflectometry

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