Patent ID: 7068044

Claim:
A physical layer device that communicates over a cable, comprising: a cable tester that determines a cable status, which includes an open status, a short status and a normal status, wherein said cable tester includes: a pretest module that senses activity on the cable and that selectively enables testing depending upon said sensed activity; and a test module that is enabled by said pretest module, transmits test pulses on the cable, measures a reflection amplitude, calculates a cable length, and determines said cable status based on said measured amplitude and said calculated cable length; and a polarity detector that communicates with said cable tester and that detects a polarity of at least one pair of the cable, wherein said test module senses activity on a first Pair of said cable, enables testing if activity is not detected for a first period, and enables testing of said first pair if, during said first period, activity is detected on said first pair and is subsequently not detected on said first pair for a second period after said activity is detected.