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uk.telecom.voip (UK VOIP) (uk.telecom.voip) Discussion of topics relevant to packet based voice technologies including Voice over IP (VoIP), Fax over IP (FoIP), Voice over Frame Relay (VoFR), Voice over Broadband (VoB) and Voice on the Net (VoN) as well as service providers, hardware and software for use with these technologies. Advertising is not allowed.

Modem over VOIP



 
 
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  #1  
Old February 4th 06, 07:30 PM posted to uk.telecom.voip
John Dann
external usenet poster
 
Posts: 9
Default Modem over VOIP

Anyone tell me what the present status of trying to pass data via an
analogue modem over a VOIP 'line' might be please?

Just to clarify: In the traditional POTS world, one can use a standard
analogue modem at a remote location connected to a data source to pass
data across the phone network to a central PC (also fitted with a
suitable modem of course). Can this yet be done reliably over a VOIP
connection with a suitable adapter?

JGD
  #2  
Old February 4th 06, 08:22 PM posted to uk.telecom.voip
Thomas Kenyon
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Posts: 148
Default Modem over VOIP

John Dann wrote:
Anyone tell me what the present status of trying to pass data via an
analogue modem over a VOIP 'line' might be please?

Just to clarify: In the traditional POTS world, one can use a standard
analogue modem at a remote location connected to a data source to pass
data across the phone network to a central PC (also fitted with a
suitable modem of course). Can this yet be done reliably over a VOIP
connection with a suitable adapter?

JGD


The is an ITU specification called ITU V.150.1 specifically for this
purpose.

This hasn't been implemented in Asterisk yet (I don't know if it's been
implemented in any software) or any ATA that I'm aware of.

So it's more a case of, It will happen at some point but don't hold your
breath.
  #3  
Old February 5th 06, 03:03 AM posted to uk.telecom.voip
Brian Gregory [UK]
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Posts: 208
Default Modem over VOIP

"John Dann" wrote in message
...
Anyone tell me what the present status of trying to pass data via an
analogue modem over a VOIP 'line' might be please?

Just to clarify: In the traditional POTS world, one can use a standard
analogue modem at a remote location connected to a data source to pass
data across the phone network to a central PC (also fitted with a
suitable modem of course). Can this yet be done reliably over a VOIP
connection with a suitable adapter?


Since you have a broadband connection wouldn't it make more sense to set up
a VPN over the internet instead?

--

Brian Gregory. (In the UK)

To email me remove the letter vee.


  #4  
Old February 6th 06, 04:52 PM posted to uk.telecom.voip
Martin Lukasik
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Posts: 27
Default Modem over VOIP

Anyone tell me what the present status of trying to pass data via an
analogue modem over a VOIP 'line' might be please?


Can you tell me what do you need it for?
VoIP is, itself, running on the "internet", means you have to be connected
in order to make it working. And if it's working -- why do you want to
dialup?

m.


  #5  
Old February 6th 06, 05:20 PM posted to uk.telecom.voip
John Dann
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Posts: 9
Default Modem over VOIP

On Mon, 6 Feb 2006 15:52:07 -0000, "Martin Lukasik"
wrote:

Anyone tell me what the present status of trying to pass data via an
analogue modem over a VOIP 'line' might be please?


Can you tell me what do you need it for?
VoIP is, itself, running on the "internet", means you have to be connected
in order to make it working. And if it's working -- why do you want to
dialup?

Well, I thought that I'd briefly outlined the need for such a modem
link, but let me try again:

Let's say that you have an instrument at a remote location that you
wish to 'talk to' (ie pass data to and from) from a PC at a central
location. That instrument has an RS232 serial interface - OK this is a
little old-fashioned but many scientific instruments still do work
this way.

With a conventional POTS landline you simply connect your remote
instrument via its serial interface to eg a V90 modem connected to the
landline at the remote end and equip your central PC with a similar
modem. From the central PC you dial the remote modem and set up a call
to your remote instrument and the two ends can talk to their hearts'
content. But in practice there's a limit to how often you can do this
for cost and maybe other reasons - it's fine for a once daily download
of data, but the landline isn't (traditionally at least and unless
it's a leased line) an always-on link suitable for continuous transfer
of data.

But eg ADSL is always-on and VOIP could be free-per-call. Since VOIP
effectively passes a spectrum of audio signals across its link and a
modem does just the same, I was wondering whether a traditional modem
could be hooked into a VOIP setup to do the same thing, but the answer
seems to be no in practice, for the moment at least.

Of course there are other ways of achieving this functionality like
setting up a WAN across an ADSL link and have a Device Server at the
remote end, but this is potentially more complicated and expensive
than using a simple V90 modem.

JGD
  #6  
Old February 6th 06, 06:13 PM posted to uk.telecom.voip
Heimo Hetl
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Posts: 23
Default Modem over VOIP

John Dann wrote:

But eg ADSL is always-on and VOIP could be free-per-call. Since VOIP
effectively passes a spectrum of audio signals across its link and a
modem does just the same, I was wondering whether a traditional modem
could be hooked into a VOIP setup to do the same thing, but the answer
seems to be no in practice, for the moment at least.


Well, it can definitely be hooked up, at least physically. Whether it
actually works, and if so, at which throughput rates, depends on the
analog signal quality the whole chain from your local media gateway (or
ata box) to its remote counterpart can provide.

If most of it is under your control, you may be lucky. If you can live
with _really_ low speed connections (think 300 Baud), it will most
certainly work. Maybe this will do for simple remote data collection?

After all, fax over IP does work as well (if done properly). Your
biggest enemies are jitter and latency. Of course, don't even dream of
using a codec other than G.711.

If you hook up a modem to a tradfitional POTS line, its audio will be
converted to G.711 and back as well. The only difference is the network
between the converters which is usually of undefined quality on the
Internet, as opposed to the traditional TDM grid. So just give it a try
- and let us know of the results.

cheers
Heimo


--
You never ask questions when God's on your side.
  #9  
Old February 6th 06, 07:12 PM posted to uk.telecom.voip
Bob Evans
external usenet poster
 
Posts: 22
Default Modem over VOIP

In article , John Dann
wrote
But eg ADSL is always-on and VOIP could be free-per-call. Since VOIP
effectively passes a spectrum of audio signals across its link and a
modem does just the same, I was wondering whether a traditional modem
could be hooked into a VOIP setup to do the same thing, but the answer
seems to be no in practice, for the moment at least.

Of course there are other ways of achieving this functionality like
setting up a WAN across an ADSL link and have a Device Server at the
remote end, but this is potentially more complicated and expensive
than using a simple V90 modem.


Am I the only one to think that the notion of taking some intrinsically
digital data, converting it to an "analog" form and then immediately
re-digitising it to pass through a "digital" channel is slightly
perverse?

--
Bob Evans
  #10  
Old February 6th 06, 07:43 PM posted to uk.telecom.voip
Tim Bray
external usenet poster
 
Posts: 89
Default Modem over VOIP

Thomas Kenyon wrote:
Unless you want to think about using a VPN and something similar to a
modem server. (lets you map a virtual COM port (or tty) to a remote
machines COM port).


This is the best way to do it. It is really easy to do on Linux
machines. There is some commercial software that does it on windows.

I have yet to see a `modem bank service provider` yet though.

Tim
 




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