wayer@oracle.uucp (William Ayer) (03/20/91)
At a demonstration of the NeXT machine two years ago, Jobs suggested
that the DSP chip would allow programmers to create a software modem / fax
machine (very little hardware would be needed i.e. a cable). Was this
suggestion wishful thinking, or could such a beast exist?
--
William B. Ayer Work: (415) 358-7248
Email: wayer@oracle.com Home: (415) 508-1663scott@mcs-server.gac.edu (Scott Hess) (03/21/91)
In article <1991Mar19.214415.27530@oracle.com> wayer@oracle.uucp (William Ayer) writes:
At a demonstration of the NeXT machine two years ago, Jobs suggested
that the DSP chip would allow programmers to create a software modem / fax
machine (very little hardware would be needed i.e. a cable). Was this
suggestion wishful thinking, or could such a beast exist?
Well, this is technically possible. Basically, the internals of a modem
are a DSP chip plus some glue logic [ :-) ].
The problem is that in a modem the DSP is dedicated, while on the NeXT
it isn't quite so dedicated. The amount of work needed to be done
outside the DSP is greater on the NeXT than when it's off on that
serial port. The DMA support isn't really there, etc, etc. You could
upgrade your DSP memory (that would fix most of those types of
problems), but in general I think it's a close one as to whether or
not you can run a 9600 baud modem off the DSP.
On the other hand, 2400 should be fully realizable. I've seen schematics
(don't ask me for them - I can't give them out), and I know that people
have played with it. One problem is that you need FCC approval to
connect this beast to a phone line. With a modem, it's not such a
big deal - after all, there's not alot of memory/disk storage in
a modem, so it's not really a very good computing machine. Meanwhile,
hooking up an interface through the DSP to a NeXT (arguably a fair
computing machine), the possibilities are ripe for infamous 'blue
boxes'. These would be boxes which could be used to rip off the
phone company (free long distance, etc). Not so good.
Lastly, I think that a DSP modem is sort of silly. Fact: You're
going to be spending >$3500 (after shipping/taxes) on a machine,
and realistically most people will be up over $4000. Fact: The
box to hang between the DSP and the phone line is probably going
to cost $$$ - combined with the appropriate driver software, I'd
be surprised if it were under $150 (very surprised at that). Fact:
kermit is free. Stuart is nearly so. (Last) Fact: A Hayes
compatible MNP 5 modem costs under $200 nowdays for a decent one,
lower if you shop.
I just don't see the need for a DSP modem. It's too much of a
bother, and inflexible to boot. When you can get a cheap modem
and the software to drive it most anywhere, it's silly to try for
another solution which will not be so cheap and will be hardwired
to your machine (you won't need new drivers when NextStep3.0
comes out if you buy a modem).
Later,
--
scott hess scott@gac.edu
Independent NeXT Developer GAC Undergrad
<I still speak for nobody>
"Simply press Control-right-Shift while click-dragging the mouse . . ."
"I smoke the nose Lucifer . . . Banana, banana."kls30@duts.ccc.amdahl.com (Kent L Shephard) (03/21/91)
In article <1991Mar19.214415.27530@oracle.com> wayer@oracle.uucp (William Ayer) writes: > > At a demonstration of the NeXT machine two years ago, Jobs suggested >that the DSP chip would allow programmers to create a software modem / fax >machine (very little hardware would be needed i.e. a cable). Was this >suggestion wishful thinking, or could such a beast exist? > >-- > William B. Ayer Work: (415) 358-7248 > Email: wayer@oracle.com Home: (415) 508-1663 It could exist. Someone needs to write the software and design a telephone interface. KeNT -- /* -The opinions expressed are my own, not my employers. */ /* For I can only express my own opinions. */ /* */ /* Kent L. Shephard : email - kls30@DUTS.ccc.amdahl.com */
jjfeiler@nntp-server.caltech.edu (John Jay Feiler) (03/22/91)
Speaking of using the DSP as a modem, does anyone out there know where to find onformation on the protocall for modems? I.e. CCITT V.22, V.22bis, V.32 V.32bis, etc. How about info on group III fax protocall. What about the various MNPs. I may even get around to making a DSP-modem, if I can ever find out what it need to do to actually send & receive data..... Thanks in advance JoHN FeILeR
kls30@duts.ccc.amdahl.com (Kent L Shephard) (03/22/91)
In article <SCOTT.91Mar20171454@mcs-server.gac.edu> scott@mcs-server.gac.edu (Scott Hess) writes: >In article <1991Mar19.214415.27530@oracle.com> wayer@oracle.uucp (William Ayer) writes: > At a demonstration of the NeXT machine two years ago, Jobs suggested > that the DSP chip would allow programmers to create a software modem / fax > machine (very little hardware would be needed i.e. a cable). Was this > suggestion wishful thinking, or could such a beast exist? > >Well, this is technically possible. Basically, the internals of a modem >are a DSP chip plus some glue logic [ :-) ]. > >The problem is that in a modem the DSP is dedicated, while on the NeXT >it isn't quite so dedicated. The amount of work needed to be done >outside the DSP is greater on the NeXT than when it's off on that >serial port. The DMA support isn't really there, etc, etc. You could >upgrade your DSP memory (that would fix most of those types of >problems), but in general I think it's a close one as to whether or >not you can run a 9600 baud modem off the DSP. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 9600 baud is not the hardest thing in the world for a 56k DSP. Why now do you think it is possible to have a dedicated modem with a slow DSP and not a fast one? 9600 is "possible". To be realistic a 25Mhz 56k should be able to handle 19200 baud. Remember you can do real time spectral analysis with monster scope. That is a lot harder than determining a bit from a phase modulated signal. (The person I told FSK. I meant PM- phase modulation). > >On the other hand, 2400 should be fully realizable. I've seen schematics >(don't ask me for them - I can't give them out), and I know that people Simple A/D converter and a D/A converter with a phone line interface. you could get away with bits for conversion because the frequency that is modulated is not that high. Remember that phonse have almost no frequency response above 3.5Khz. The DSP can handle sampling rates up at least 88Khz. You can get a telephone interface from Radio Shack. So the hardware is not difficult. >have played with it. One problem is that you need FCC approval to ~~~~~~~~~~~~~ See above. The interface is FCC approved. Your hardware connects to the interface and never to the phone line. The interface used to cost around $10-$15. Now if you want to build your own interface, then you need FCC approval. Why bother, when it's done for you already. >connect this beast to a phone line. With a modem, it's not such a >big deal - after all, there's not alot of memory/disk storage in >a modem, so it's not really a very good computing machine. Meanwhile, >hooking up an interface through the DSP to a NeXT (arguably a fair >computing machine), the possibilities are ripe for infamous 'blue >boxes'. These would be boxes which could be used to rip off the >phone company (free long distance, etc). Not so good. Yes, if you generate the right tones you could rip them off. But you don't need a NeXT for that you can do that with an old eight bit machine. > >Lastly, I think that a DSP modem is sort of silly. Fact: You're >going to be spending >$3500 (after shipping/taxes) on a machine, >and realistically most people will be up over $4000. Fact: The >box to hang between the DSP and the phone line is probably going >to cost $$$ - combined with the appropriate driver software, I'd >be surprised if it were under $150 (very surprised at that). Fact: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Even if it costs $300 that IS cheaper than a comparably price 19200 baud beast. >kermit is free. Stuart is nearly so. (Last) Fact: A Hayes >compatible MNP 5 modem costs under $200 nowdays for a decent one, ~~~~~~~~~~~~~ 2400 baud, 9600 is still a minimum of $400. >lower if you shop. > >I just don't see the need for a DSP modem. It's too much of a >bother, and inflexible to boot. When you can get a cheap modem ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Inflexible how? Once you have the modem hardware built it can function as a FAX with a software change. Or an answering machine. You could even build a detect feature in the software that would distinguish FAX, modem, voice. >and the software to drive it most anywhere, it's silly to try for >another solution which will not be so cheap and will be hardwired >to your machine (you won't need new drivers when NextStep3.0 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Maybe, maybe not. A lot of software is broken under the 1.0 - 2.0 upgrade. Your communication program could break the same way anything else could. >comes out if you buy a modem). > >Later, >-- >scott hess scott@gac.edu >Independent NeXT Developer GAC Undergrad ><I still speak for nobody> >"Simply press Control-right-Shift while click-dragging the mouse . . ." >"I smoke the nose Lucifer . . . Banana, banana." -- /* -The opinions expressed are my own, not my employers. */ /* For I can only express my own opinions. */ /* */ /* Kent L. Shephard : email - kls30@DUTS.ccc.amdahl.com */
mfi@serc.cis.ufl.edu (Mark Interrante) (03/23/91)
In article <2cqt023R06Lj01@JUTS.ccc.amdahl.com> kls30@DUTS.ccc.amdahl.com (Kent L. Shephard) writes: >Simple A/D converter and a D/A converter with a phone line interface. >you could get away with bits for conversion because the frequency that >is modulated is not that high. Remember that phonse have almost no >frequency response above 3.5Khz. The DSP can handle sampling rates up >at least 88Khz. You can get a telephone interface from Radio Shack. >So the hardware is not difficult. Hi, I am interested in such a product, so I called up two radio shacks and asked for a telephone interface (even described the desired functions) Neither had heard of it. Can anyone please provide a more specific reference for this beast? Thanks, Mark ----------------------------------------------------------------------------- Mark Interrante Software Engineering Research Center mfi@beach.cis.ufl.edu CIS Department, University of Florida 32611 ----------------------------------------------------------------------------- "Imagine what it would be like if TV actually were good. It would be the end of everything we know." Marvin Minsky
eps@toaster.SFSU.EDU (Eric P. Scott) (03/23/91)
In article <1991Mar21.235024.974@nntp-server.caltech.edu> jjfeiler@nntp-server.caltech.edu (John Jay Feiler) writes: > does anyone out there know where to find >onformation on the protocall for modems? I.e. CCITT V.22, V.22bis, V.32 >V.32bis, etc. How about info on group III fax protocall. What about the >various MNPs. CCITT is part of the ITU, a United Nations agency. Libraries with government documents repositories should have the CCITT fascicles. Group III FAX uses CCITT V.29 (ter?) modems. MNP 2-4 are described in the CCITT V.42 spec, MNP 5 and above are Microcom proprietary. -=EPS=-
fjs@nntp-server.caltech.edu (Fernando J. Selman) (03/23/91)
kls30@duts.ccc.amdahl.com (Kent L Shephard) writes: >In article <SCOTT.91Mar20171454@mcs-server.gac.edu> scott@mcs-server.gac.edu (Scott Hess) writes: >>In article <1991Mar19.214415.27530@oracle.com> wayer@oracle.uucp (William Ayer) writes: >> At a demonstration of the NeXT machine two years ago, Jobs suggested >> that the DSP chip would allow programmers to create a software modem / fax >> machine (very little hardware would be needed i.e. a cable). Was this >> suggestion wishful thinking, or could such a beast exist? >> >>Well, this is technically possible. Basically, the internals of a modem >>are a DSP chip plus some glue logic [ :-) ]. >> >>The problem is that in a modem the DSP is dedicated, while on the NeXT >>it isn't quite so dedicated. The amount of work needed to be done >>outside the DSP is greater on the NeXT than when it's off on that >>serial port. The DMA support isn't really there, etc, etc. You could >>upgrade your DSP memory (that would fix most of those types of >>problems), but in general I think it's a close one as to whether or >>not you can run a 9600 baud modem off the DSP. >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >9600 baud is not the hardest thing in the world for a 56k DSP. Why now >do you think it is possible to have a dedicated modem with a slow DSP >and not a fast one? 9600 is "possible". To be realistic a 25Mhz 56k >should be able to handle 19200 baud. Remember you can do real time >spectral analysis with monster scope. That is a lot harder than >determining a bit from a phase modulated signal. (The person I told FSK. >I meant PM- phase modulation). >Simple A/D converter and a D/A converter with a phone line interface. >you could get away with bits for conversion because the frequency that >is modulated is not that high. Remember that phonse have almost no >frequency response above 3.5Khz. The DSP can handle sampling rates up >at least 88Khz. You can get a telephone interface from Radio Shack. >So the hardware is not difficult. It is my impression that when you say 9600 baud you mean 9600 bps. This is not a trivial difference. As you correctly stated, the phone lines have an upper cut-off of 3.5 kHz, thus they can handle 2400 bauds but not 9600. The modems that claim 9600 bps are actually 2400 baud modems using a modulation scheeme called QAM, Quadrature Amplitude Modulation, in which they can pack 4 bits [sic] in each period of the 2400 baud wave. This scheeme is the one used in all V.32 modems. But these modems also need to do echo cancellation to operate in full duplex mode, and I understand (but I might be wrong) that this have to be done in hardware, otherwise the local modem could not "understand" what the remote modem is saying because of the echoes from his own transmissions. I believe this to be the reason why Telebit modems are assymetric, that is not full duplex, they have not been able make an echo cancelation scheeme that works at the higher frequencies they use. Telebit uses an scheeme called DAMQAM, where QAM is the same as above, and the DAM part refers to a propietary scheeme used to send information through multiple channels that are constantly monitored. All this is possible because of the use of the glue chips mentioned above. This is why I think that to connect a simple black box with a CODEC chip to the DSP port and to then try to implement a high speed modem in hardware is impossible, IMHO. - Fernando >/* Kent L. Shephard : email - kls30@DUTS.ccc.amdahl.com */
markus@tubkom.prz.tu-berlin.de (Markus Rebensburg) (03/24/91)
>In article <1991Mar19.214415.27530@oracle.com> wayer@oracle.uucp (William Ayer) writes: >> >> At a demonstration of the NeXT machine two years ago, Jobs suggested >>that the DSP chip would allow programmers to create a software modem / fax >>machine (very little hardware would be needed i.e. a cable). Was this >>suggestion wishful thinking, or could such a beast exist? >> >>-- >> William B. Ayer Work: (415) 358-7248 >> Email: wayer@oracle.com Home: (415) 508-1663 > >It could exist. Someone needs to write the software and design a >telephone interface. > KeNT It exists !! At the CBIT fair in Hanover(Germany) a prototype of the modem was shown at the NeXT stand. It includes a group III fax modem, a data modem with 2400 baud and an answering machine with some nice feature. A normal phone and an accustic mailbox will be included in the next release. The hardware fits in a machbox. You can get more informations from i.link GmbH Phone: +49 30 781 70 55 EMail: Piers_Walter@ilink.de or Piers_Walter@ilink.uucp Markus (Markus Rebensburg) -- --------------------------------------------------------------------- Markus Rebensburg eunet : markus@tubkom.UUCP
michael@ewa.cs.ucla.edu (michael gersten) (03/26/91)
kls30@duts.ccc.amdahl.com (Kent L Shephard) writes: >9600 baud is not the hardest thing in the world for a 56k DSP. Why now >do you think it is possible to have a dedicated modem with a slow DSP >and not a fast one? 9600 is "possible". To be realistic a 25Mhz 56k >should be able to handle 19200 baud. Remember you can do real time >spectral analysis with monster scope. That is a lot harder than If the DSP is this powerful, could it handle the PEP protocol? I know, PEP is slower than 19200, but no one I talk to speaks 19200, and several speak PEP. Michael