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About DSL modem lights - SpeedTouch modems

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The operational status of DSL modems is usually indicated by lights (LEDs). Modems models vary in detail, of course, but typically they have lights to indicate power, the status and activity of the DSL line, and the status and activity of connections to your computer, whether by ethernet or by wireless.

For example, Thomson 585 modems have five lights on the front (Power, Broadband, Ethernet, WLAN, and Internet) and four lights on the back (status of each of the four ethernet ports).

Information is communicated by the colour of the lights and whether they are steady or flashing. Activity on a line is often indicated by flickering when the line is active.

Here's a summary of how to read the lights of a Thomson 585 v7 (other models are similar):


Power light

The power light should be steady green. If it is unlit, there's a power problem or the unit is completely inoperative. Check that the modem is plugged in and switched on.

If the power light is red or amber, the unit has discovered a problem with its hardware or software. Try power cycling the unit, ie., unplugging the unit from power and disconnecting it from all cables, waiting more than 5 seconds (for capacitors to discharge), and then connecting it to power again. If the power light goes green, then connect cables. Otherwise, if the red or amber Power light persists, the unit will likely have to be replaced.

Ethernet light

The ethernet light should be green (steady or flickering) if there is at least one ethernet cable connected to a powered-on computer. Green indicates that ethernet communication is possible. Ethernet traffic is indicated by flickering of the light.

To check individual cables, most SpeedTouch modems have green LEDs at the back of the modem were the ethernet cables plug in. The LED there will be green (and flicker with activity) if ethernet is active on that particular cable. Note: If you are having problems and find any of those back-side ethernet LEDs flashing at a steady rate (on-off-on-off...), it indicates a hardware problem that requires service (but try power-cycling).

Broadband (DSL) light

The Broadband should become steady green within a few minutes after power-up or restart, indicating that the unit has detected a DSL signal and is able to synchronize with it; the unit is 'in sync'.

During the process of obtaining DSL synchronization, the Broadband light will flash green. If it flashes indefinitely, there is a problem.

If you previously had a working connection and nothing has changed at your location (eg., no new devices attached to your phone line), try power cycling your modem (see above). If that doesn't work, likely it's an external problem; best to wait 10 minutes and see if it clears up. Sometimes the modem needs to be power-cycled for it to notice a line that has returned to service.

If you are installing for the first time, here are possible solutions:

  • Make sure there is no filter on the line to your modem. The modem must be plugged directly into the phone line.
  • Make sure all other devices at your location are connected through DSL line filters.
  • If problems persist, try temporarily disconnecting all other devices from your phone line.

If you can find a working internet connection (perhaps a friend or at an office or library), you can check online with NCF to see if anyone else is experiencing problems. If not, best to send a problem report to the NCF office.

WLAN (Wireless) light

The WLAN light flashes to indicate activity (like the Ethernet light). The colour of the light indicates the security mode of the wireless service: green is highest security, using WPA encryption; amber is medium security, using WEP; and red indicates no security (anyone can use your wireless without providing a password). The light is unlit if wireless is disabled (turned off).

For information about configuring wireless and enabling/disabling it, please consult the modem manual for your unit.

Internet light

The internet light is steady green when the Central Office has accepted your modem's login and password and is ready to provide internet service via DSL to your modem. If the light remains red or unlit, there is a problem.

If your unit was able to log in earlier and you've made no changes, a red light likely means that there is a temporary network problem (at the Central Office or NCF) making it temporarily impossible to check your login and password. Best to just wait for the problem to be fixed. You may need to power-cycle or restart your modem for it to notice that service has been restored. If you can get online elsewhere (eg., at an office or library), you can check the NCF web site to see if others are experiencing problems, and if not, report the problem (such problems are almost always noticed quickly).

If you are installing for the first time and the DSL light is green but the Internet light is red, likely your unit hasn't been configured with a correct login and password. Check the configuration instructions for information about configuring.

Beyond the lights

Lights can indicate only a small amount of information. To learn more about what your modem is doing, you can view your DSL usage log (this link is also available from the NCF StartPage, under 'Internet Access'). Often the pattern of connect/disconnects will be revealing.

It's also possible to log into your modem (there is a computer with a UNIX operating system in there) using a web browser, and then view its event log. For information about the modem's event log, consult the modem manual for your modem model.

Background information: Stages of DSL Connection-Making

This page explains how a DSL modem connects to the internet.

Start up

After powering up, a DSL modem typically goes through these stages:

  1. Self-testing
  2. DSL sync
  3. Authentication
  4. In-service


Upon power-up, a modem typically performs tests to detect proper operation of its hardware and to detect problems in its software and data. This stage usually takes only a few seconds.

DSL sync

The first stage of connecting to the internet is to obtain a 'link level' DSL connection to the Central Office or DSLAM. Once established, the modem will use this connection to carry internet traffic.

Obtaining and maintaining a good DSL connection to the Central Office or DSLAM is crucial to good performance. To maximize performance, the modem tries to sense the quality of your phone line and adapt to conditions. The most basic requirement is obtaining DSL synchronization (detecting and locking onto the DSL signal).

Things that can go wrong at this stage, in order of most likely first, include:

  • no connection to the phone line
  • electrical noise from other devices on your phone line
  • low power signal caused by being far from the Central Office or DSLAM
  • electrical noise on the line from sources outside your location
  • problems at the Central Office or DSLAM.


Once a DSL connection has been made with the Central Office or DSLAM, it can be used by the modem to talk with the NCF authentication server. This requires your modem to identify itself with a login and password (for security and billing purposes). Your modem can do the authentication for you but of course it must have been programmed with the correct information.

The most common problems at this stage include:

  • not having correct login and password information programmed into your modem
  • temporary network problems that prevent the authentication server from confirming the log-in information that your modem provides to it.


Finally, when the DSL connection is up, your modem has been authenticated and granted access, it tells your computer that it is ready. Your computer can then send and receive information from the internet. Requests go from your computer to your modem (via ethernet cable or wirelessly), then from your modem to the network (via your phone line), then over the network to whichever web site computer you specified.

Connecting to your modem

Your modem also looks for connections to your computer(s) via its ethernet ports or, if equipped and enabled, via wireless. The establishment of these links goes through similar stages as described above for DSL. Ethernet connections are usually quite reliable and trouble-free, but wireless connections can suffer from interference with other wireless signals. There are only eleven channels allocated for wireless use in Canada and in most urban locations, especially in apartment buildings or townhouse complexes, there can be twenty or more networks within range of your computer, which can make interference hard to avoid. For more information see About wireless.

Once you have a 'link level' connection to your modem, you can use a web browser to communicate with the computer inside the modem, just as if it were a web site on the internet.