What does a broadband filter do?

Question

My ISP - Orange - tells me that the reason my internet connection keeps dropping may be because of a faulty filter. Could this be correct? And what is the function of the filter?

Answer 1

Your talking about DSL, right?

DSL sends both data and analog voice over the same set of twisted pair wires. The filter blocks the data signal from messing with the voice signal.

It blocks everything above around 3Khz from getting to the phone.

Answer 2

The filter is a box which connects to the socket, it has sockets for telephone and modem/router connection. You can connect a dsl modem/router to it, and a telephone if you wish. It splits the digital dsl signal from the analogue telephone signal and passes each to the correct socket. You need one of these for the dsl equipment, which can also connect a phone. If you have any other equipment connected to the same line you need one filter for each. Any phone, fax, modem or answering machine needs it's own filter. If you have all the filters you should have, disconnecting one filter (and it's equipment) at a time and running your connection while you dial the line from a mobile (you don't need to answer the calls) will prove if a filter is faulty. If none of them affects this, disconnect one, swap it for your dsl one and try again.

Answer 3

A filter is necessary because once your line is activated with Broadband it carries 2 signals - an analogue (phone) signal and a digital (broadband) signal which are both carried at different frequencies. In order to receive both of these signals clearly you must connect all of your devices which normally plug into a phone socket into a Broadband filter. It is this feature of Broadband which allows you to use the Internet connection whilst on the phone or receiving faxes.

Answer 4

Your standard phone line carries two types of data. Analog & Digital.

The Analog is your voice! (The 'phone' part).

The Digital is the Broadband signal.

The Filter or Splitter simply 'splits' the two types of data & sends them to their respective host. (i.e. Your phone or your DSL modem, depending on the data!)

A faulty filter could cause a connection loss, try replacing it as advised by your ISP.

Answer 5

It's a bandpass filter that separates the low frequency band of voice frequencies, typically 100 -> 3.4kHz from the much higher frequency carrier of the broadband digital stream.

This is to prevent the digital intelligence being corrupted by the voice frequencies.

By the way, you need a filter on EVERY telephone socket in your house, not just on the socket to which the router/modem is connected. If you have a Sky Box or your cordless phone base unit is plugged in to a BT socket, you need a filter on those sockets as well.

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Maplins do them - they are typically £7 each.