OT: DSL causing noise on answering machine

Is the answering machine plugged into mains power?

Does the answering machine, when recording, cause noise to other phones? i.e. Let the answering machine record a voice message and while the recording is going on, pick up the phone and listen to it. Is there noise? OR is the noise only in the tape?

I had the same problem with a cordless phone/answering machine. 2 filters in series fixed the problem. I have noticed that some filters work better than others. The filters i purchased were locally (AU) badged, so I cant tell you a brand.

Hello PTW,

Yes, via a two-prong wall wart transformer. No ground pin.

It doesn't, the noise is only on the tape. So bad that if I went to pick up the mail, forgot to turn the DSL modem off and a long distance call came in I can barely understand the message.

You can't record a phone conversation with this one. But when the answering machine has kicked in and a phone gets picked up it will continue for a few seconds, then go offline and stop its tape. There is never noise in the picked up phone receiver from the machine or from DSL.

I have a hunch that it's poorly designed. When I simulated a DSL filter it rolled off around 10kHz so part of the first DSL channel leaks through to some extent. Maybe the pre-amp in the machine is so lousy that it has no dynamic range and intermodulates. Thing is, I am not the only one with that problem, seems lots of machines do that. Possibly I have to build myself a better DSL filter. Great, another project...

Regards, Joerg

Hello Andy,

Forgot to mention that I had tried two filters in a row. But you've got a point there in that these filters might not be so good. Haven't measured one yet (the analyzer needs calibration) but I picked the schematic of a typical passive inline filter and simulated that. This did not look very nice, roll-off starting at 10kHz so that much of the first DSL channel might be smack dab right in the passband. This could intermodulate in the machine's amp. But if that were the case the designer of that amp would need to brush up on analog circuit design, big time.

Before going back and forth to the store until I find an answering machine that's properly designed I might just roll my own custom DSL filter. Heck, maybe I could sell them as DSL answering machine filters because I am not the only one with this problem.

Regards, Joerg

"Joerg" a écrit dans le message de news:Nd5_f.64133$ snipped-for-privacy@newssvr13.news.prodigy.com...

Maybe DSL HF leakages beats with the premag oscillator. We now have such pb with a machine I designed in the before DSL times. Here DSL beats with the sampling rate. The trick is obviously a better (differential mode) HF filtering.

Hello Fred,

Thanks for the hint. I didn't even think about the premag oscillator (heck, when is the last time I fixed a cassette player...?).

It seems most of the tape answering machines in the stores around here contain the same electronics and I don't want a RAM based one because of the shaky power grid. So, I guess I'll have to roll my own DSL filter now. Oh well, at least it's something analog and thus my home turf.

Regards, Joerg

Maybe you can find one with battery backup. My cheap RAM-based machine contains 3 AAA batteries for backup.

Maybe subscribe to Voice Messenging from the phone company ?:-)

Also: If you have a separate line for business you can write off all the expenses... I have three lines, one personal, two for the business.

Another option is Call Forwarding to your cell phone, and Voice Messenging there.

...Jim Thompson

Hello Matthew,

I have a few devices with that. It's one more thing to include in the half-yearly smoke detector battery change ritual. Plus sometimes they don't like glitches, issue dirty resets and stuff. My faith in the ability of the average design engineer to design a clean uC reset has dwindled over the years :-(

Regards, Joerg

Hello Jim,

Most phones do not have a blinky light for that. Friends who have VM often don't call back, later saying "Sorry, I forgot to check my VM".

I wanted to. We have four lines coming into the house but Pacific Bell could only get one to work to spec :-(

Can't beat under 3c/min. What I do is buy long distance cards. Always one in the kitchen (doesn't get written off) and one for biz calls in the office (gets written off). This way there is hardly anything on the phone bill other than the usual line charge and taxes, and maybe very few 'local long distance' calls but many of those are non-biz. BTW, this new Brother fax/scannner/copier works just dandy on that one line. It is quite immune to DSL. Man, now I've got lots of additional space in the office since it combined three machines into one spot.

Don't have a cell phone (yet). They don't work well out here. But I'll have to pretty soon. Unfortunately VirginMobile discontinued all their no-frills Nokias and stuff. Big mistake, methinks. When I find one again I'll buy that.

How are you son and his wife doing?

Regards, Joerg

I have der "blinkinty light" phones ;-) CID, CID waiting, call forwarding, call following, message center controlling, all kinds of features. I own the phones, so I don't pay a fee for them. $28.95/line + $5-$7/month total LD (all lines).

I had that problem initially since this was a new build area.

BTW: Reminds me... make sure your line is a "real" pair and not one of those multiplexed muthas ;-)

Son is putting weight back on and is doing well... his only remark, which struck me interesting... when he takes chemo the tumor site "hurts"... I guess chemo is really good at targeting now-a-days.

Just got a call... he wants to know if the family Easter celebration will still happen... the whole family at our house... he wants to come!!!

As for the wife, she's a trooper just like my wife, when the going gets tough, the tough get going... Duane has often said, when certain "management" decisions were made, "I married my mother" ;-)

...Jim Thompson

Hello Jim,

Interesting. We have AT&T phones, digital and quite safe. They contain so many features that I never had the time to get to the ground of it so maybe they could do it.

Anyway, I placed another lowpass there now, let's see when the next call comes in with the modem on. Fred wrote that it could be mixing with the premag oscillator. Pretty sad that the machine doesn't have enough immunity against this but it might indeed be the explanation for what's happening.

I just like the fact that I don't have to dial in to retrieve messages. Come back in, light blinks, hit the play button and listen while hanging up the jackets and putting the dog leashes away.

I'd have no control over that but probably it isn't since DSL comes via that same line. And it goes above 1Mb/sec regularly.

Chemo has come a long ways. My wife used to be a cardiac nurse and she said they had to watch hearts for enlargement in the old days. Sometimes they had to make the call to cut off the chemo. They had to triage between reigning in the cancer and preventing a cardiac crisis. I guess that has gotten a lot better these days.

This is good news. As to "married to my mother" I can relate to that. Sometimes when my wife talks to my mom she says "See, your mom says I was right about this".

Regards, Joerg

I have one of those spinning globes that display Caller ID info. Has worked like a charm for the past year. Hooked up DSL, and now the globe will randomly beep and display garbage every 8-16 hours. Hooked up a DSL filter, no change. Hooked up a second filter in series, no change.

:-(

Hello,

Sometimes connections get loose on the line and then a slight diode action at those points can cause intermod between the DSL channels and some of that stuff can end up in the audio baseband. But that should be visible on an analyzer.

Also, watch out that not a single phone is connected sans filter. This happened here on install, I simply forgot the one in the basement. That caused a serious racket on all the other (filtered) phones until I placed a filter down there as well. After that it was quiet except for the answering machine.

If that globe is connected to mains power a good common mode choke might help.

Regards, Joerg

I did not notice if you have a wireless router or not. If you have, could the noise be from the 2.4 ghz router signal and not DSL line stuffat all??

Doh! I have not filtered the basement phone.

Thanks

Hello John,

I do but it is mostly turned off (no power).

Regards, Joerg

You are welcome. What happens is that many phones have protection diodes. As non-linear devices these mix all the DSL carriers like a margarita blender and some of the results can end up in the spectrum where caller ID is transmitted.

Regards, Joerg

Ok, folks, after rigging up filtering in front of that thing that muffles everything above 10kHz by more than 50dB the noise is still almost the same. Guess it's time to buy some other models and try them out, one by one, until one works. Must be pretty sad circuitry in there.

Regards, Joerg