Reports, in 10 MHz clock ticks, how long elapsed between the start of the most recent Time-Domain Reflectometry (TDR) cable test and the collision that terminated it, or 0 if no TDR test has run. Since TDR timing is proportional to cable distance to a fault, an admin can use this value to estimate roughly how far down the Ethernet cable a break or short is located. For example, a nonzero tick count after running a TDR test on a suspect link tells the admin where along the cable run to start physically inspecting for damage.