Hi,

I have two sites where a fax modem is connected to the same line as our
ADSL (via the filter where a handset would normally go).

At both sites any fax activity usually knocks out the ADSL for the
duration of the fax. Is this to be expected or should it work OK? Surely
it should be the same as a voice call as far as the line is
concerned. Any suggestions appreciated.

Thanks,

-- 

John Devereux

In article , John Devereux 
 wrote
>I have two sites where a fax modem is connected to the same line as our
>ADSL (via the filter where a handset would normally go).
>
>At both sites any fax activity usually knocks out the ADSL for the
>duration of the fax. Is this to be expected or should it work OK?

No, it should work.

I know of several sites where the same line is used for both ADSL and 
fax and without any interaction.

I'd start by finding out if the filter is doing its job.  I'd also be 
looking to see what other equipment may be connected to the same line, 
etc.

-- 
Bob Evans

Bob Evans  writes:

> In article , John Devereux
>  wrote
>>I have two sites where a fax modem is connected to the same line as our
>>ADSL (via the filter where a handset would normally go).
>>
>>At both sites any fax activity usually knocks out the ADSL for the
>>duration of the fax. Is this to be expected or should it work OK?
>
> No, it should work.
>
> I know of several sites where the same line is used for both ADSL and
> fax and without any interaction.
>
> I'd start by finding out if the filter is doing its job.

OK, will try some different filters.

Actually one location was working OK until we had to change the
modem. Perhaps the new one has a higher output level, or contains a lot
of high frequency harmonics.

> I'd also be looking to see what other equipment may be connected to
> the same line, etc.

Nothing (in either case).

Thanks,

-- 

John Devereux

In article , John Devereux 
 wrote
>Actually one location was working OK until we had to change the
>modem. Perhaps the new one has a higher output level, or contains a lot
>of high frequency harmonics.

Possible I suppose.  But (a) the modem has no business to be putting any 
frequency >4KHz onto the phone line; and (b) one would expect a simple 
passive low-pass filter (such as an ADSL splitter) to attenuate high 
frequencies in both directions.

-- 
Bob Evans

John Devereux wrote:
> Hi,
> 
> I have two sites where a fax modem is connected to the same line as our
> ADSL (via the filter where a handset would normally go).
> 
> At both sites any fax activity usually knocks out the ADSL for the
> duration of the fax. Is this to be expected or should it work OK? Surely
> it should be the same as a voice call as far as the line is
> concerned. Any suggestions appreciated.

Couple of years since I've used fax from dialout modem and
it didn't work as receiving modem wouldn't accept connection
from my outdated fax card, but others would as fax2email
service I use accepted and I received the copy via email.

I've not used dialup for a while but there was a change to
bt connection requirements reducing maximum ren I think
from 6 to 4 (but happy to be corrected) which meant my extra
bell and extensions caused problems. These were dropped from
my bill at the time (many years ago) but I now see they have
somehow reappeared.

Neither fax nor dialup has caused problems otherwise except
for when there has been a line fault.

David

Bob Evans  writes:

> In article , John Devereux
>  wrote
>>Actually one location was working OK until we had to change the
>>modem. Perhaps the new one has a higher output level, or contains a lot
>>of high frequency harmonics.
>
> Possible I suppose.  But (a) the modem has no business to be putting
> any frequency >4KHz onto the phone line; and (b) one would expect a
> simple passive low-pass filter (such as an ADSL splitter) to attenuate
> high frequencies in both directions.

It's very strange, but is repeatable at two sites with two different
modems. It seems to me I could try cascading two filters as well.


-- 

John Devereux

In article , John Devereux 
 wrote
>It's very strange, but is repeatable at two sites with two different
>modems. It seems to me I could try cascading two filters as well.

You should not need to do that.  Is there any possibility that the 
filters you are trying are so cheap that the ferrites inside them are 
saturating due to line current (or perhaps peak ringing current) ?

-- 
Bob Evans

Bob Evans  writes:

> In article , John Devereux
>  wrote
>>It's very strange, but is repeatable at two sites with two different
>>modems. It seems to me I could try cascading two filters as well.
>
> You should not need to do that.  Is there any possibility that the
> filters you are trying are so cheap that the ferrites inside them are
> saturating due to line current (or perhaps peak ringing current) ?

I think they are both AAISP supplied ones. One is almost certainly. I
have never actually bought one. They just come with various routers.

It *is* possible that it is just the ringing causing the disconnect,
rather than the fax data tones.


-- 

John Devereux

John Devereux wrote:
> I have two sites where a fax modem is connected to the same line as our
> ADSL (via the filter where a handset would normally go).
> 
> At both sites any fax activity usually knocks out the ADSL for the
> duration of the fax.

I've never had problems either inbound or outbound. My router is plugged 
directly into the BT ADSL faceplate in my NTE5 socket. My modem is 
plugged directly into the same faceplate. I have no house wiring at all.

-- 
Steve Swift
http://www.swiftys.org.uk/swifty.html
http://www.ringers.org.uk