Are dsl filters really necessary? We just installed a bunch of phone jacks in our remodeled attic and it just occurred to me I may need to dig out that box of filters that came with the dsl stuff way back when. There is a phone box thing in the attic -- maybe if I am clever I can cover everything with a single filter? The dsl modem currently plugs into a jack on another floor.
Are dsl filters really necessary?
- Thread starter rw120555
- Start date
If possible, the best thing to do is to find where the wire enters your home from your NID box, and to install a whole-house splitter at that point. You will need to connect the DSL modem there at the splitter, though. You'd then run an Ethernet line from that DSL modem to wherever you want a data connection.
There is a recommended limit to the number of phone jacks that you should have with filters.
There is a recommended limit to the number of phone jacks that you should have with filters.
Yes, the DSL filters are absolutely necessary.
POTS (Plain Old Telephone Service) equipment such as phones, fax machines, and regular modems generate impedance in the telephone wiring when they are used. This impedance then interferes with the DSL signal over your phone line, degrading it to the point where it can even temporarily interrupt DSL service. This interruption will keep up as long as you are talking on the phone, sending faxes, using the modem, etc.
What DSL filters do is filter out this impedance so that you may use your phone without interfering with the DSL signal. This is why the instructions for DSL filters say to put them between any phones/fax/modems you have and the wall outlet. The other purpose of DSL filters is to keep the high frequency DSL signal from reaching your POTS device. The high frequency DSL signal tends to cause noise on POTS devices, which can make for a very aggrivating phone call or slow regular modem connect sppeds.
The problem with DSL filters is that using too many of them starts to cause capacitance in the phone line. This capacitance will again start to interfere with the DSL signal. Generally, the recommended limit is 4 filters.
The best solution though is to use a whole house splitter, as cmetz mentioned. This splitter seperates the DSL and POTS frequencies right at the point of entry to your house, eliminating the need for a filter at every phone. Phone companies don't like to do this because they have to send a technician to install it, and he may have to rewire some of the phone jacks in your house. This costs them money, so they would rather send you some filters and have you put them on all your POTS devices. If you are familiar with telephone wiring and are comfortable working with it, you can also install the splitter yourself.
POTS (Plain Old Telephone Service) equipment such as phones, fax machines, and regular modems generate impedance in the telephone wiring when they are used. This impedance then interferes with the DSL signal over your phone line, degrading it to the point where it can even temporarily interrupt DSL service. This interruption will keep up as long as you are talking on the phone, sending faxes, using the modem, etc.
What DSL filters do is filter out this impedance so that you may use your phone without interfering with the DSL signal. This is why the instructions for DSL filters say to put them between any phones/fax/modems you have and the wall outlet. The other purpose of DSL filters is to keep the high frequency DSL signal from reaching your POTS device. The high frequency DSL signal tends to cause noise on POTS devices, which can make for a very aggrivating phone call or slow regular modem connect sppeds.
The problem with DSL filters is that using too many of them starts to cause capacitance in the phone line. This capacitance will again start to interfere with the DSL signal. Generally, the recommended limit is 4 filters.
The best solution though is to use a whole house splitter, as cmetz mentioned. This splitter seperates the DSL and POTS frequencies right at the point of entry to your house, eliminating the need for a filter at every phone. Phone companies don't like to do this because they have to send a technician to install it, and he may have to rewire some of the phone jacks in your house. This costs them money, so they would rather send you some filters and have you put them on all your POTS devices. If you are familiar with telephone wiring and are comfortable working with it, you can also install the splitter yourself.
Thanks! Here is the setup: in the attic, we have a telephone network interface box. All of the new lines are connected to it. Could I just open up that box, unplug the clip for the dsl line, attach a filter, replug it in? I suppose I might have to leave the interface box open, but no big deal. Will that do the trick? I still have the original dsl line outlet downstairs, which I assume would be unaffected by this. This is a home business line so it isn't used throughout the house, just the attic and the existing room where my wife was working.
Alternatively -- if I wanted to move my dsl modem upstairs -- what exactly is a "whole house" splitter, and how would I use it in this setup? Maybe put some sort of adapter on the clip at the telephone box, with a filter on one side and no filter on the other?
It might also be tempting just to switch which line the dsl is on, e.g. move it to the fax line which people don't normally speak on.
Alternatively -- if I wanted to move my dsl modem upstairs -- what exactly is a "whole house" splitter, and how would I use it in this setup? Maybe put some sort of adapter on the clip at the telephone box, with a filter on one side and no filter on the other?
It might also be tempting just to switch which line the dsl is on, e.g. move it to the fax line which people don't normally speak on.
Fallen Kell
Diamond Member
- Oct 9, 1999
- 6,153
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They are only necessary if you don't like getting disconnected from the internet every time someone calls you or you call out 
Does anyone have a link to one of these whole-line splitters, and, also, does anyone have a link to an online vedor where different telephone network interface boxes can be purchased? Thanks.
Good info in here guys.
Online you can go to BroadBandshoppe.com for filters. At the stores, RadioShack is the only store I have seen DSL Filters on the shelf.
If you don't go with one filter where your line comes in the house, it is not recommended to go beyond 5 filters. Each filter adds the equivalent of 700 feet of wire to the line, so with 5 filters you add 3,500 feet to your signal from the origin of the DSL signal. The signal is only solid for 15,000 feet so if you are located 12,000 feet away you just killed your signal.
I documented the way I have DSL in the house with no filters seen anywhere including where the line comes into the house.
I have a new Brand of Modem that has a Built-in DSL Microfilter port.
I just switched the inside pair of house phone wires with the outside pair where the wire comes into the house and left the inside pair disconnected at the box.
Then I went to the jack where I have my DSL Modem and disconnected the inside pair of phone wires and left them for a minute. Then I connected the outside pair of wires at the jack and plugged the Modem ADSL port to the jack. That makes a direct connection of the hot DSL signal to the modem without having to make a cable run. Now to give the rest of the house a filtered line so the phones work. I just plugged a regular phone cable into the Phone port on the Modem that has the built-in DSL Filter. Then I took the plug off the other end and connected the 2 inside pair of wires to the inside pair I had disconnect from the jack before. That made all the phone jacks live in the house (5 phones plus the alarm system) live again without having to put a filter at every jack.
Later to be neater I got a double gang RJ-11 wall jack so I have a plug on each line. One jack labeled ADSL and the other Labeled Phone.
I also was able to plug one of those RJ-11 splitters so I could connect the Phone and Fax machine I have by the Computer.
Online you can go to BroadBandshoppe.com for filters. At the stores, RadioShack is the only store I have seen DSL Filters on the shelf.
If you don't go with one filter where your line comes in the house, it is not recommended to go beyond 5 filters. Each filter adds the equivalent of 700 feet of wire to the line, so with 5 filters you add 3,500 feet to your signal from the origin of the DSL signal. The signal is only solid for 15,000 feet so if you are located 12,000 feet away you just killed your signal.
I documented the way I have DSL in the house with no filters seen anywhere including where the line comes into the house.
I have a new Brand of Modem that has a Built-in DSL Microfilter port.
I just switched the inside pair of house phone wires with the outside pair where the wire comes into the house and left the inside pair disconnected at the box.
Then I went to the jack where I have my DSL Modem and disconnected the inside pair of phone wires and left them for a minute. Then I connected the outside pair of wires at the jack and plugged the Modem ADSL port to the jack. That makes a direct connection of the hot DSL signal to the modem without having to make a cable run. Now to give the rest of the house a filtered line so the phones work. I just plugged a regular phone cable into the Phone port on the Modem that has the built-in DSL Filter. Then I took the plug off the other end and connected the 2 inside pair of wires to the inside pair I had disconnect from the jack before. That made all the phone jacks live in the house (5 phones plus the alarm system) live again without having to put a filter at every jack.
Later to be neater I got a double gang RJ-11 wall jack so I have a plug on each line. One jack labeled ADSL and the other Labeled Phone.
I also was able to plug one of those RJ-11 splitters so I could connect the Phone and Fax machine I have by the Computer.
Thanks DM. Not sure I understand this though:
I'd never heard about this 5 filter limit before -- seems like a non-trivial thing to be hiding from people. If you call up and say that your dsl isn't working, do they break down and send somebody to install one of these whole-house splitters or something? If I wind up having problems I will definitely check into this. Also, cable wasn't available when we got our dsl -- now that it is, maybe we should consider switching. RW
WHat exactly is the inside pair and the outside pair? Outside my house, there is this telephone box -- is there normally something inside as well? Maybe I have such a box and just don't know it. Actually, in our remodeled attic, there is a new phone box, so I think I've been able to isolate the problem and solution there. But, I'm not sure what I would do if the dsl was on our main home line -- we have so many outlets that we'd have to get zillions of filters.
I'd never heard about this 5 filter limit before -- seems like a non-trivial thing to be hiding from people. If you call up and say that your dsl isn't working, do they break down and send somebody to install one of these whole-house splitters or something? If I wind up having problems I will definitely check into this. Also, cable wasn't available when we got our dsl -- now that it is, maybe we should consider switching. RW
Most homes are pre-wired for 2 phone lines with at least a 4 wire cable. The green and red inside pair are normally run to all the jacks and live for the first line. The black and yellow outside pair is just sitting dormant if you don't have a second line. When you have DSL service you normally don't need a second line anymore. That was the case here. By disconnecting the 1st line phone wires at the box and leaving them disconnected and then re-connecting that pair at the DSL Modem it is simply moving the point at which the Phones in the house get phone service from the box outside to the Modem inside. By connecting the unused pair of wires at the Outside Box where the main line is now a Hot DSL signal line and connecting that pair to a Jack inside at the Modem, that makes the DSL signal the only thing on that wire run to the DSL Modem. I call it the "No Wire Home Run".
Dave
hey, thats the same way my house is wired with DSL. basiclly, pacbell came and HARDWIRE my house. they gave me an USB modem that reads from outter two wires. okay, on a typical phone cable, there are 4wires. the inner two are line1, and the outer two is line2. phone requires only 2 wire to function. for most typical phone, its being used by inner wires, thats why some cheap extension wires only have 2wires yet still works. anyways, the dsl modem pacbell gave me reads outter two. so tech guy came here, split the single phone line into two, for both inner and outter. bascilly using both line1 and line2, but they had a filter on line1 for all the regular phone which left dsl by itself on outter.
this was good, till i switch modem. now i have to cut a phonewire up and swap the connections. anyways, i want to get rid of this swaping method for some kinda hub or switch that does this without me manually cutting wires open. anyone know where i can get one of these?
this was good, till i switch modem. now i have to cut a phonewire up and swap the connections. anyways, i want to get rid of this swaping method for some kinda hub or switch that does this without me manually cutting wires open. anyone know where i can get one of these?
I've worked on the No Wire "Home Run" page and put a couple of pics, I will put more pics and analogies up as well.
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