1. First cut off the power supply and make sure there is no current on the line.

2. Secondly, select the ohm file or the connected detection file, and connect the two test leads of the multimeter to the terminals at both ends of the line respectively, or connect the two test pins of the line tester to the terminals at both ends of the line respectively.

3. Finally, if the multimeter shows the resistance value, or the test indicator light of the line tester is on, the line is connected; If there is no obvious change in the multimeter display screen or tester indicator light, it means that the line is open or disconnected or there are other problems.