If no short is detected after the delay, then the incident is considered a transient or false positive, and at step 330, the false short event is registered. Finally, at step 322, the controller goes back to sleep.

If, on the other hand, the short is still detected at step 310 after the delay, then the isolators 210 are opened (step 312) and the two ports 202 and 204 are electrically isolated from each other. The controller enables (step 314) the Ptest function 270 (FIG. 2), which continuously monitors the impedance of the line 200 by placing a predetermined voltage onto both sides of the isolator 210, and the Ptest function 270 may be coupled to the fault isolation controller 212 via a line 274. Diodes 280 serve to isolate the two sides of line 200 from each other during the Ptest. Ptrouble 272 verifies that both sides of 210 (isolated from each other by diodes 282) do not have abnormal impedances, and Ptrouble 272 may be coupled to the fault isolation controller 212 via a line 276. The controller then waits at step 316 until the impedance, as monitored by the Ptest/Ptrouble circuitry, returns to normal for some duration T, for example, 0.1 ms. The duration T may incrementally increase each time the Ptest is run, for example, by +100 μs the second time, then by +1 ms, +10 ms, +100 ms, +1 s, +10 s, +100 s, and so on.

Once the impedance returns to normal for duration T, the Ptest is stopped (step 318), the isolators 210 are closed (step 319) and the ports 202, 204 are again in electrical communication. The short circuit event is registered (step 320) and the controller 212 goes back to sleep (step 322).