I suppose if you're used to very poor telephone quality it might be described as a 'low level' hiss. I'm quite close to my London exchange, and am used to quite decent audio quality. The hiss from ADSL was perhaps
15dB down on the audio. So not something I'd put up with.
Oh..without a scope and a meter I cant tell you exactly what mine is, but less than that for sure.
Think say 1/4" tape machine at 7.5ips versus cassette tape.
it got a bit better when they totally remade the line back to the exchange, but its still there.
And of couyrse if 50 other people who have maybe worse and more diode like junctions are alongside MY line, then their DSL will get folded back into baseband and couple in enough to hear maybe.. its not like weakly hearing someone's conversation. Unlike voice, where maybe only one or two pairs are active ALL those subscribers have PERMANENT DSL..
If BT had any sense they would mandate straight VOIP on all lines and broadband would be a necessary precursor to voice.
The VOIP line here is split out by the router and goes straight into the PABX as well, Clean as a whistle. Unless the wife is downloading something massive, when sometimes the odd packet gets lost..
Well I don't see much call for one way cordless phones.
Easily.
The answer seems to be, they fiddle with things until the fit mechanically. They understand that the parts may be required, but not the subtlety that the order of assembly matters, as does ensuring a similar looking part that came with another bit of kit may not be a direct substitution, even if it does "fit".
The number of times I hear the intro of "I unplugged everything and put it all back together again" is amazing. Had one chap with intermittent broadband, who insisted in pulling apart his internal network and re plugging every time, because it "fixed it". I pointed out that all he was doing was the tech equivalence of a rain dance, and the only functional action that had any effect was restarting the router forcing it to remake a connection. More to the point he was likely to introduce unreliability by causing wear to all the sockets etc. (eventually got him to report a line fault, and BT fixed it).
It is probably yet another a case of "unskilled and unaware" (or the unknown unknowns if you prefer). One can comprehend some aspects of a job, like the fact the connector on the PSU should fit the socket. They may even understand the need for the voltage to match the requirements, however could still be ignorant of the supply current needing to be adequate, or the fact the polarity of the wiring of the connector might matter.
(I think I may have told the story before of gentleman who wanted to make use of a hand scanner (we are talking early 90's here) from the office machine on the secretaries desk, with his laptop. Having unplugged the scanner from the desktop (leaving its dedicated ISA interface card in her PC obviously), he was now confronted with a connector that did not fit any of the sockets on his laptop. So he chopped it off and re-terminated the lead onto a new connector! Eventually returned it the the secretary saying "this does not work", can you send it back? IIRC she phoned Logitech and told them the story. They were so amused, they sent her a free replacement!)
The customer was more than content with me adding a microfilter to it... (she had not realised there should be one on every phone, rather than just the one using the same socket as the router)
While entirely possible, the effect of other ADSL connections would tend to be across the full allocated DSL spectrum. The effect with radio interference tends to be concentrated on specific spot frequencies within the spectrum (see Dave's pictures above for a nice illustration)
Looking at it from the other direction, I can observe a 25% reduction in downlink data rate at some times of night, necessary to maintain a usable SNR.
I heard of someone who used a similar 'technique' for upgrading their
486 to a Pentium.Owain
Seems to me the "filter" is a band splitter. It ensures that the phone gets only LF signals, and that the modem only gets the band intended for ADSL use. Where the word "filter" applies is stopping the phone putting and RF out, on the line, towards the house wiring. There may not be much of that but neither is there much ADSL signal by the time you get it.
But then your fixed line phone wouldn't work in a power cut. We just changed broadband provider and took their phone service too. But I made sure it was POTS and not VOIP before signing up.
No, the voice socket is connected to the phoneline via a low-pass filter to cut-out the data signals, but the ADSL socket on a filter is wired
*direct* to the phoneline ... there may be a separate high-pass filter within the ADSL router to cut-out the voice signals, or it might just "tune them out" as a consequence of tuning-in each of the 3kHz wide frequency bins.
I've fished a few USB plugs out of Ethernet ports. ;-(
Yup, True.
Most probably, yes.
;-)
Talking of that. Stepdaughter has had some dropouts on her TalkTalk ADSL broadband service and that is seen simultaneously by other people using the net there at the same time. The problem is getting her to contact Tech Support because she's frightened about being talked into doing something she wouldn't have done had she known the bigger picture (like when they have go people to do a factory OS restore and lost them all their data). Dad thought he had lost all his mails after talking to a Tech Support line but I just went round there and deleted the 'test' account they had got him to make. ;-)
NO!
I've seen so stuff but I've don't think I've seen anything quite as bad as that.
Nice.
Cheers, T i m
Its a simple lowpass filter. The only splitting it does is physical to give an unfiltered output to the modem and a filtered one to the phone(s).
Simpler than I thought, then, ta.
There is a good chance that the "POTS" line is VoIP. We had DSLAMS that combined VoIP and DSL on the same subscriber modules. Of course they will be backed up, etc. We also had subscriber modules that had 2M lines that went into the switches but that was supposed to be a stop gap. These were the technologies that 21cn is based on,.
so what? use a mobile!
We only have cheapo Tesco PAYG jobs and there's essentially no signal here in the Kentish mountains.
Our exchange is not unbundled if that makes any difference. I don't care if its VoIP from the exchange onwards. But I want to know that in the event of a power cut I'll still have phone service.
I did check with their technical people but of course you can never be quite sure who you're talking to. Point is I've installed nothing here (no software or hardware) to support VoIP from here. Some providers appeared to hint that that would be needed.
Right. So its only purpose is to remove noise from the line when using a phone. Just why have you been arguing black is white for the past couple of days?
well it isnt.
Probably because that is almost the opposite of what I said!
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