Phone line filter - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: March 17, 2022, 07:40:44 pm
content: Hi,how can I remove noise the phone line which is also used to bring in the Internet line? I tried the usual filter that comes with the router but nothing...The phone line itself has lots of audible noise whenever the phone is used and it varies in volume and type. From barely hearable (rarely) to very loud. And from loud crackling noise to general hiss type to sometimes even other voices/conversations in the background. To the point that most of the time the phone line cannot be used (either cannot hear what the other person is saying or they cannot hear me).In case the topology matters, the line comes in the flat into the first phone socket where the phone is plugged in. Then the same line carries on to another room (10 meters away) where the router is plugged in.I tried plugging in the phone with and without filter in either one of the two sockets but no difference.Any suggestions for perhaps different/better/special filter? Or any other suggestion?Thank you

author: jonpaul
author_rank: Super Contributor
timestamp: March 17, 2022, 07:58:44 pm
content: Suggest to get a different /better DSL filter.Anything you connector a phone line must be rated for such use and regulatory compliance.Beware of -48V battery and 90V ring tone on POTSJon

author: fourtytwo42
author_rank: Super Contributor
timestamp: March 17, 2022, 08:22:53 pm
content: Sometimes noise is generated by dirty contacts in the jacks, some contact cleaner and a few insertions/extractions often do the trick, don't forget if there is a connector on the phone itself and on the router to clean these too.If you only have one telephone are you sure it is not faulty ? could you borrow another to try it ?It sounds like you may be confused with how to use DSL filters, it is essential that any telephone connected to a line with a DSL modem/router on it is only connected VIA a dsl filter otherwise the telephone will cause severe attenuation of the dsl signals.

author: TheMG
author_rank: Frequent Contributor
timestamp: March 17, 2022, 11:25:03 pm
content: The fact that you are sometimes hearing other voices that's what is called "crosstalk" and would more than likely be due to a problem outside your flat. The usual cause would be a cable with deteriorated and/or wet insulation or a problem at a splice point.I suggest calling up the phone company as that's a problem with their infrastructure. You can't magically filter that stuff out on your end (garbage in, garbage out).Chances are this is also likely impacting your DSL performance.

author: ricko_uk
author_rank: Super Contributor
timestamp: March 18, 2022, 02:20:08 am
content: Thank you allI tried cleaning the contacts and I do have a filter on the socket that has the phone plugged in.I will try other ADSL filters. But it sounds like it might be crosstalk like TheMG suggested given the very old wiring. After I made the post I remembered that the intercom has the same issue so that might be the cause.Thank you

author: Kleinstein
author_rank: Super Contributor
timestamp: March 18, 2022, 08:05:25 am
content: The "crosstalk" can also be EMI. So a signal coming in via a radio signal of some sort. What type of phone is it ? The problem could also be insider the phone.

author: SeanB
author_rank: Super Contributor
timestamp: March 18, 2022, 02:25:52 pm
content: Clean all sockets, plugs and leave phone and filter unplugged, and test speed of line. If it improves then the phone, or the wiring to the phone, is the issue, but likely nothing will change, telling you it is a telco issue, likely a cable that is wet and letting in water. Can be anywhere between your socket and the exchange, so keep on complaining about noise on the phone line, as the telco will try to fix that, and fixing the noise on POTS voice will likely fix the DSL issues as well, likely a connection box that is wet, or a wet cable, or dirty connections in the DSLAM.