Broadband connections and Microfilters

OK, let's see if I can get you to save yourself some money on calling me out!

This is about the importance of microfilters to a broadband connection.

The microfilter is the little plastic box which plugs into your phone line and then your phone and/or broadband modem plugs into that.
So what does it do and why is it important?

When you talk on the phone your voice is converted into electrical signals which run at a particular frequency. Think of it as someone playing a tune on a double bass.

The broadband connection also uses electrical signals but these run at a higher frequency; that's a bit like someone playing a tune on a violin.

Both of these can be going on at the same time, just like our two string players, but it gets a bit confusing so in order to hear the individual tunes properly you'd need some sort of filter. You could use a filter which blocks higher frequencies then you'd hear the double bass OK, or you could use one which blocks low frequencies so you could hear the violin.

It's the same with the microfilter. The telephone connection doesn't want to hear any of the broadband stuff and the broadband doesn't want to have the telephone interfere with its connection! The microfilter keeps these two signals apart.

So what happens if it's missing?

Maybe you're already guessing this - or maybe you've already experienced it...

Without a filter, if your broadband is running and you use the phone you'll get a VERY noisy phone call! If you're happily using the broadband and someone phones you, you're likely to lose the broadband connection.

So now the crunch... how many and where?

How many depends on your telephone setup. I used to have quite a few installed but then I reorganised my 'phone wiring so now I just need one!

The basic rules are:

1. Every piece of phone equipment must go through a filter at some point.
2. The broadband signal must go through one (and only one) filter
   

That first rule doesn't necessarily mean that every phone needs its own filter; you could have a single filter going to a splitter which runs several phones. And remember that a telephone device includes anything which plugs into the phone system; fax machines, answer machines, credit card machines, even your old computer modem, if you still use that.

So consider the following situation:

Two phones and a fax machine each have a filter and the broadband connection also goes into one of those filters.

Of course, if the extension sockets themselves ran off a filter, the number of filters required would be reduced as in the next layout:

Now all the phone connections are brought together at a single point (the splitter) and that goes through the single microfilter.

Getting the filters right is very important but, with a little thought and understanding, this isn't too tricky. If you don't get it right, your system simply won't work properly!

But remember it's only actual devices that need filters - an empty extension socket doesn't matter... until you plug something into it!