Check for faulty home internal phone wiring

Published 12/05/2004 15:46   |    Updated 18/01/2008 10:33

Can I check for a possible fault with my internal phone wiring?

Poorly installed home phone wiring or poor quality phone extension leads (often with a flat rather then round cable profile) are the most common causes of slow broadband speeds. This is because they are more prone to electrical interference, which causes BT Broadband to reduce data speeds to compensate. You can test for this as follows:

  1. If you have a phone master socket like the one in the photo below (that is, square with a horizontal groove halfway down it and removable upper and lower cover), we recommend you remove the lower cover as shown, taking care not to dislodge any wiring. Do not remove the upper cover. This will reveal a test socket on the right-hand side. This connects directly to the exchange, bypassing your home phone wiring and extensions.


  1. Plug your router or modem directly into this test socket via a microfilter
  2. Re-check your connection speed as per Step 3 in the previously viewed answer, ensuring you refresh your browser page first. If your connection speed has increased significantly, this indicates a likely fault or interference source within your home wiring. If it remains unchanged, this indicates either no fault, or the fault or interference is more likely to be in eircom's wiring or in your local exchange.
  3. If you do not have a master socket of the type shown above, or cannot plug your router or modem directly into it, we recommend you minimise the length of any phone wiring between your master phone socket and your router or modem, avoid the use of flat or aluminium phone extension leads (go for round copper cable instead, which may sometimes be marked 'DSLMax-compatible'), and route cables to avoid areas of electrical interference such as near power cables, digital phones, microwave ovens, Christmas tree lights, high-wattage equipment, halogen lighting and so on.

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