Don't know what you use over there?, but here ADSL filters have one input, and two separate outputs (using different sockets) - one ouput is low-pass filtered, and feeds the phone, the other is high-pass filtered and feeds the ADSL.
Each phone in the house has a filter feeding it, fltering the HF ADSL signal out, and the ADSL modem has one feeding it, filtering out the LF audio and ringing tone.
An alternative is to have just ONE filter, directly where the phoneline comes in, and fed all the phones in the house off the phone output of that single filter, and the modem off the ADSL output from it.
I use a combination of both - the incoming line is split two ways - one way goes to an ADSL filter and feeds all the telephone sockets in the house, the ADSL output is unused. The other output of the splitter feeds directly to my attic (where I am now), and where another ADSL filter is used, to feed both the modem and a phone next to it, just because the phone output was there, and it saves me walking across the room to where the normal phone socket is
So I've got just two filters, for six phones and one modem.