DTMF over RTC

[Fred Bartoli]

That's not in my line but I've inherited an old project from where I
previously worked.

The system uses a PC+MODEM to manage some remote instrument.
The modem is there only to get the phone line interface and dialog with the
intrument through DTMF exchange.

There were several thousands instruments installed and about 100 PC servers.
Now the chosen modem doesn't exist anymore and we need to find a
replacement.

You'd think, any modem will do.
Maybe. Anyway I remember we had problems with DTMF receiving (don't remember
precisely which) and propagation time through all the windows layers.

Any known good reference for a PCI modem?

 

[Joseph2k]

That's not in my line but I've inherited an old project from where I
previously worked.

The system uses a PC+MODEM to manage some remote instrument.
The modem is there only to get the phone line interface and dialog with
the intrument through DTMF exchange.

There were several thousands instruments installed and about 100 PC
servers. Now the chosen modem doesn't exist anymore and we need to find a
replacement.

You'd think, any modem will do.
Maybe. Anyway I remember we had problems with DTMF receiving (don't
remember precisely which) and propagation time through all the windows
layers.

Any known good reference for a PCI modem?

Well, now you are in the specialty weird modem business. It may be possible
to abuse current compliant modems to do what you want (no guaranties, it
may well not be possible). Study the properties of the command set
carefully.

 

[Joseph2k]

That's not in my line but I've inherited an old project from where I
previously worked.

The system uses a PC+MODEM to manage some remote instrument.
The modem is there only to get the phone line interface and dialog with
the intrument through DTMF exchange.

There were several thousands instruments installed and about 100 PC
servers. Now the chosen modem doesn't exist anymore and we need to find a
replacement.

You'd think, any modem will do.
Maybe. Anyway I remember we had problems with DTMF receiving (don't
remember precisely which) and propagation time through all the windows
layers.

Any known good reference for a PCI modem?

Bloody mess. Come to think about it there were only a few DTMF
gerenator/receiver chips ever made. I do not know of any still in
production. However you may be able to buy a DSP which can do the job and
any patented code for the process should be expired by now. It wouldn't
take much of a DSP by todays standards either.

 

[David Harmon]

On Tue, 07 Feb 2006 06:09:54 GMT in sci.electronics.design, Joseph2k

production. However you may be able to buy a DSP which can do the job and
any patented code for the process should be expired by now. It wouldn't
take much of a DSP by todays standards either.

If I recall correctly, the author of the article in the current
Circuit Cellar is doing it with a PIC.

 

[OBones]

As far as DTMF receiver are concerned, the 8870 is still made, I just
bought a few recently.

 

[Nel]

hi fred,
May be a custom design could solve your problem which can accept DTMF
tones through telephone link and will send to the pc using some
interface. If you can elaborate in some detail then may be we can help
you !

 

[Fred Bartoli]

"Fred Bartoli"

That's not in my line but I've inherited an old project from where I
previously worked.

The system uses a PC+MODEM to manage some remote instrument.
The modem is there only to get the phone line interface and dialog with the
intrument through DTMF exchange.

There were several thousands instruments installed and about 100 PC servers.
Now the chosen modem doesn't exist anymore and we need to find a
replacement.

You'd think, any modem will do.
Maybe. Anyway I remember we had problems with DTMF receiving (don't remember
precisely which) and propagation time through all the windows layers.

Any known good reference for a PCI modem?

Sure we could custom design something. Dead easy, but we won't have as many
servers and they are connected to the phone network, so they have to have
homologation, and this will be sold in many countries. Way too much hassle,
cost and time.

One way is to buy 50 modems at random and try. We're sure to find one
suitable in the pile.
Just thought somebody may already know for sure a suitable one.

 

[[email protected]]

One way is to buy 50 modems at random and try. We're sure to find one
suitable in the pile.
Just thought somebody may already know for sure a suitable one.

You may have better luck with modems (possibly PCI, more likely little
brick-like serial modules) sold for embedded applications - they cost a
bit more than those found in flavor of the week store PCs, but are a
bit more stable in their specifications and functionality.

 

[Fred Bartoli]

You may have better luck with modems (possibly PCI, more likely little
brick-like serial modules) sold for embedded applications - they cost a
bit more than those found in flavor of the week store PCs, but are a
bit more stable in their specifications and functionality.

Hmmm, good idea. Any brand (or better reference) on top of your head?

 

[Michael A. Terrell]

"Fred Bartoli"


Sure we could custom design something. Dead easy, but we won't have as many
servers and they are connected to the phone network, so they have to have
homologation, and this will be sold in many countries. Way too much hassle,
cost and time.

One way is to buy 50 modems at random and try. We're sure to find one
suitable in the pile.
Just thought somebody may already know for sure a suitable one.

Have you tried ebay? If they are discontinued, people tend to dump
them into the surplus channels.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Rich Grise]

That's not in my line but I've inherited an old project from where I
previously worked.

The system uses a PC+MODEM to manage some remote instrument. The modem is
there only to get the phone line interface and dialog with the intrument
through DTMF exchange.

There were several thousands instruments installed and about 100 PC
servers. Now the chosen modem doesn't exist anymore and we need to find a
replacement.

You'd think, any modem will do.
Maybe. Anyway I remember we had problems with DTMF receiving (don't
remember precisely which) and propagation time through all the windows
layers.

Any known good reference for a PCI modem?

All of the modems I've seen only use DTMF for dialing. Are all of these
things supposed to be able to talk to each other, or is there one "master"
and 99 "slaves?"

If you're going computer-to-computer, then you don't even need modems -
just serial interfaces. There might be something called a "short-haul
modem", but you'd have to look that up - I saw one about 20 years ago, and
don't know if they make them any more either.

What are you trying to accomplish? Do you have to replace a bunch of
adapters or modems? Why not just make it all ethernet?

Thanks,
Rich

 

[Fred Bartoli]

All of the modems I've seen only use DTMF for dialing. Are all of these
things supposed to be able to talk to each other, or is there one "master"
and 99 "slaves?"

No, 100 masters, 10000s slaves (custom instruments part of which is already
installed), dispersed all over the world.

If you're going computer-to-computer, then you don't even need modems -
just serial interfaces. There might be something called a "short-haul
modem", but you'd have to look that up - I saw one about 20 years ago, and
don't know if they make them any more either.

What are you trying to accomplish? Do you have to replace a bunch of
adapters or modems? Why not just make it all ethernet?

My guess is ethernet or serial interfaces won't do over 5000 km.

I guess I've now found the *key* word: answering machine. I've now
identified 2 modems that (should) provide the functionality if it works.
None of these directly available in France.

Now I have to hope they'll work. At $10-15 some modems seem, not
surprisingly, to not work as advertised.

 

[OBones]

An OLITEC PCI card, can do answering machine, they do it with the
provided software.
And if configured correctly, it can detect ringtones and record the
received sound, but not send at the same time, it's only half duplex.
There are whole bunch of APIs under Win32 for this, it's a bit complex,
but it works.

 

[Zak]

Fred Bartoli wrote:

Well, now you are in the specialty weird modem business. It may be possible
to abuse current compliant modems to do what you want (no guaranties, it
may well not be possible). Study the properties of the command set
carefully.

Some 'winmodems' show up as an audio device in Windows - they can
actually be another channel to the sound card on cheapo modems.

DTMF decoding in software shouldn't be too hard.


Thomas