Quick question on phone extension

[DME43]

Ok, heres the problem. I have only one telephone socket in my house (it didnt even have one when we moved in ) and I need a extension of about 23 metres to the bedroom as well as having that socket.
What I intend to do, is get a splitter (to make the socket into two) and connect the phone to it then the DSL filter to the other socket to make it look something like this:

                   
|Wall socket| -----Splitter----Phone
                           ----extension lead------DSL filter------router--PC

I have brought a splitter from a one pound shop and put it where I wanted it and when i used the phone there was hissing sounds coming through. I've put this down to the quality of the product. I have looked at buying this But just in case, ive posted here to ask if there will be interference.
I think you are suppose to put the DSL filter before the splitter. The only problem with this I have is I dont have a DSL cable which is 20 metres long and not really willing to buy another one.

EDIT: I will definitely in the future need to use the telephone on that line which goes into my room (25m away) is there any connector i would need to buy in the future to be able to use the telephone? I just really confused now :p

Thanks

[DME43]

Ok, I've thought about it a bit more.
What i have come up with is this:

|wall socket|----DSL filter----Splitter (DSL remains untouched)-----first socket on splitter(wire 30m long. jacks on this wire will be from telephone to RJ11 connection---router---pc

---second socket on splitter is telephone

i've asked my mum, and she said shes not worried about not having a telephone connection in the other room, so i guess im alright there. Only thing thats bugging me now is if the setup above will give any interference or not

[johnwill]

I don't really understand your diagram, since it appears you're putting the DSL modem on a filter, which is wrong.

Basic rule, ALL phone equipment EXCEPT the DSL modem must have a filter.