Make sure all the cables related to the modem are plugged in and firmly inserted. This includes the modem's power cord, the cable from the modem to the computer, and the cable from the modem to the outlet. To be sure a connector is properly inserted, disconnect and reconnect it. Check to see if the cables have been cut, chewed, or otherwise damaged.

If you have any hubs or routers, check their cables and power supplies. If you have more than one power supply available for a type of hub or router, try swapping the power supplies. A defective power supply may affect network traffic.

Cycle the power on your DSL modem by turning it off for a few minutes then turning it back on.



If your ADSL line was installed by an eircom technician then you may have a DSL filter already built into your wall. Check the phone plate in the wall and if there is a phone connection and a DSL connection then you do not need to use a microfilter. Connecting one will cause the DSL light to flash or go off.



Make sure you have connected the modem to the master phone socket in the premises (otherwise known as the drop point, where the phone line enters the premises). DSL Synchronisation can only be guaranteed up to the drop point. It is the customer's responsibility to maintain any cabling beyond the master socket.



Extension leads can cause degradation of the broadband signal which is very sensitive to electrical interference. Excessively long extension cables and those of a poor quality will cause problems for your broadband connection. Only use the short supplied grey ADSL line cord.

If your computer can not be connected to the router using the supplied yellow Ethernet cable then avoid using extended telephone cables. As an alternative try either of the following:

  • Purchase and an extended Ethernet cable known as a CAT5E Patch cable. Such cables can be purchased from computer stores and made up to 100m in length.

  • Upgrade to a wireless router. For additional information on wireless routers click here.



Every item of telephony equipment that is connected to the ADSL phone line must have a filter connected to the wall socket first, even if the device is not currently being used. If something is connected to the phone socket without a filter then the DSL light on the modem will probably flash and you may very well notice a lot of noise on the line when you use any of your phones. This noise will go away if you turn the modem off.

If you have a digibox (e.g. NTL/Sky Digital) make sure you have connected a single filter along the phone cable between the digibox and the phone socket. Digital boxes can interfere with the broadband signal on a telephone line.

If you need a filter then there should only be one connected to each socket. For example:

INCORRECT: Socket > Microfilter > extension lead > Microfilter > ADSL Line Cord > Modem

CORRECT: Socket > Microfilter > ADSL Line Cord > Modem

Click here for a comprehensive guide on how to correctly install ADSL Microfilters as well as various installation setups and scenarios.



Make sure you don't have too many devices connected to one line. All phone lines only have a certain amount of power going through them, this power is measured in RENS (Ringer Equivalency Number). REN is the load a typical analog phone or other device imposes on the line when the phone rings.

Each line has on average four RENS available and every item of telephony equipment uses some of these RENS. Most telephony equipment unless otherwise stated uses one REN so the maximum amount of items you can have on one telephone line is four. Any more than this may cause the DSL light to flash or go off. Depending on your type of line you may have less than four RENS available.



If you have a monitored house alarm you will need to arrange an technician installation with your alarm provider.

Telephone lines Private Branch eXchange (PBX) equipment require a technician installation, as this equipment is not readily compatible with broadband.


If any of the above steps have resulted in a solid DSL light then please click here.

If you still do not have a solid DSL light click here.


BT Ireland