DTMF over RTC

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.

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.

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

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

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

"Fred Bartoli" a écrit dans le message de news:43e71c60$0$628$ snipped-for-privacy@news.free.fr...

the

servers.

remember

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.

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?

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

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

is

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

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.

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.

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