If several cables are not connected, several lights not turn on respectively. If less than two cables are conntected, none of the lights is on. If two ends of a cable is disordered, for example NO. 2and NO. 4, then displays on: Main tester: -4-5-6-7-8-G; Remote tester: 1-4-3-2-5-6-7-8-G If two cables are short circuited, neither of the corresponding lights is on of the remote tester while main tester remains unchanged. If three cables, including three, are short circuited, none of the corresponding liaghts is on. If test patch panels or wall plate outlels, two cables which can match each other (RJ45) be connected to the tester. If test cables of the same axes, BNC turns on when the cable works. (The product printed words depending on the batch, but this does not affect use) Color:As Shown Material:ABS Package Contents: 2 * Network Cable Tester Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.