What is a Line Tester?

Line Testers are used to test for faults in telephone systems, computer networks, and other metal lead circuits. It is an important instrument for low voltage system installation and maintenance of cabling systems


An important tool for engineers and technicians to test for faults and to maintain existing cable systems or a deployment of a new cable system. Designed to be able to keep the user away from a high voltage as well as being able to ensure that there is no problem in the cable system during the installation of a new cable system or maintaining and troubleshooting existing cable systems.

Why do you need a Line Tester?

Ensuring that subscribers are not disconnected from the world due to a cable fault in one of the lines is important for any telecommunication company. With a Line Tester, you will be able to detect a fault in the cable that needs to be fixed, test telephone lines and check line pairs. This will allow the subscribers to continue using the quality service that the telecommunication company is providing as they are able to maintain the cable line for them to use.

Selecting a Line Tester

All Line Testers have a basic telephone function which includes dial, redial, talk and hook. Fault test detection includes an insulation test, line break test, and earthing test. Other things that can affect your decision when buying a Line Tester is the measurement range of the device.

  • Do you need a big measuring distance? 1 to 3km

Extra features included in the device may also affect your decision. Things such as:

  • Design – How it is laid out and the looks
  • Extra wires to test other cable lines, these may include a USB cable, coaxial and alligator clips. More specifically used in multi-function testers
  • Size – made to be portable
  • Weight – designed to be light

There are many types of Line Testers in the market right now and it is difficult to pick from so many. But at GAOTek, we mainly focus on telephone line testers which may narrow down your search. As there are many features and functions in a Line Tester, be sure to double-check the specification that meets your required specifications that are needed in your line of field


Each device is different, and it is recommended that you read the instructions and understand how to use the device.

Insulation test

The main usage of this device is to test for faults in the line. One of the tests is the insulation test. The Line Tester will, under normal circumstances will display with either a few LED lights blinking or display a resistance value on an LCD display, usually up to 10MΩ. Any resistance lower than 10MΩ will normally mean that there is a fault in the line, meaning there might be bad insulation. Any value that is over 10MΩ will mean that there is no problem in the line and is fit for telephone and data services.

Line Test

This will allow the device to test whether the line is broken or not. Usually will be indicated on the device via either LCD display, LED lights or a sound coming from the device. Best to read the instruction to know how the line test is operated.

Earth Test

Using the clamps that come with the device. The black clamps will clamp on the earth line and the red clamps to the test line. Once connected, the device will test the earth insulation to see whether it is fit for purpose. Each device might test differently, so please read the instructions.


During a voltage test, if there is a high AC voltage in the line, the device will show you either with LED lights on the device or LCD display. Remove clamps as quickly as possible and take care of yourself as it can be dangerous.


As a Line Tester is a hand-held device, the battery needs to either be charged via the charger that comes with the device or change to a new lithium-ion battery. Each Line Tester will have a different way to indicate that it is low on battery.

Browse All Our Line Testers

If you can't find what you are looking for please feel free to contact our knowledgeable staff who will be happy to help you find the best Line Tester for your needs.