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routing VoIP through a regular phone line

 
 
P Gentry
Guest
Posts: n/a
 
      09-09-2004
"C3" <_> wrote in message news:<41404ae0$0$3710$(E-Mail Removed) u>...
> > Connect to Linux box via internet and have that Linux box provide a
> > dial tone so that the internet conncected host can then place a
> > "standard" PSTN voice call?

>
> That's correct.
>

[snip]

OK. Two problems:
a) how to "pipe" the sound card's output to the modem
b) how will the modem "transmit" this output to a _phone_

I'll only look at the second as it makes the first pretty much moot.

Modems are DTE devices -- _data_ terminal equipment.

Modems (_mo_dulator/_dem_odulator) use the analog _circuit_ facilities
of the POTS (ie., PSTN) to make a connection to another DTE at the far
end -- phones are not DTE's.

Two modems connected to each other via POTS use a terminal emulator
for human use. Thus all the terminal emulation options available in
modem software packages.

Modems can also be used to dial into a network (connecting to another
DTE device) and have that far end "plug" you into the network. This
is normally done with PPP -- point-to-point protocol. PPP is a
"generalized" protocol that can carry (encapsulate/frame) many link
layer protocols. That's why you see things like PPPoE and PPPoATM.
We won't go into the details of wire signaling, etc.

Point is that a modem is a (digital) _data_ device, not an analog
transmitter despite the fact that it uses the analog (voice) circuit
facilities of the "phone company".

The voice _facilities_ of the phone companies would be available with
an interface card that speaks FSO/FXO. Acquiring something as mundane
as a dial tone is not s easy as you might think. No need to go into
boring details (and their many variations) -- just know that modems
cannot utilize analog _voice_ facilities.

Faxes are another hardware interface that uses the _circuit_
facilities of POTS. Faxes _pre-date_ computers -- sometime in the
1930's IIRC and using the grandfarther of today's hi-res drum
scanners. That's why the term "fax/modem" -- a modem is not a fax
interface device without extra hardware.

"Voice" modems have minimal ability to process a voice signal --
namely record or playback a "voice stream". With software they can be
used to build suprisingly sophisticated (and large) voice mail
systems. In both cases this is a dial-in capability -- not dial-out.
Well, not entirely true, as these modems could be used for messaging
services, like _sending_ pager text.

For all this, modems still cannot establish and carry on a full duplex
_voice_ connection like a simple handset! But then they weren't
designed to do so.

If what you propose were possible, you would be able to sit at the
Linux box, strap on a mic'ed headset, and dial your neighbor who picks
up their phone handset, and chatter away. Ever picked up your handset
when a modem is at the other end "calling"?

I've taken liberties and shortcuts galore, but hopefully you have some
sense of _why_ your setup will not work -- the idea is OK but the
hardware is against you

hth,
prg
email above disabled
 
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C3
Guest
Posts: n/a
 
      09-09-2004
The only news to me is that voice modems are not capable of performing the
very limited task needed of them.

I always believed that voice modems are simply modems that can receive a
signal through a 3.5" minijack and pass it onto the phone line, and also to
send out the sound from the phoneline onto another 3.5" minijack plug. These
two can be connected to the input and output of a soundcard.

The only thing left is to dial the number, that's just an ATDT away, isn't
it?

Aren't voice modems capable of this?


cheers,



 
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Floyd L. Davidson
Guest
Posts: n/a
 
      09-09-2004
http://www.velocityreviews.com/forums/(E-Mail Removed) (P Gentry) wrote:
>"C3" <_> wrote in message news:<41404ae0$0$3710$(E-Mail Removed) u>...
>> > Connect to Linux box via internet and have that Linux box provide a
>> > dial tone so that the internet conncected host can then place a
>> > "standard" PSTN voice call?

>>
>> That's correct.
>>

>[snip]
>
>OK. Two problems:
>a) how to "pipe" the sound card's output to the modem
>b) how will the modem "transmit" this output to a _phone_


The sound card's output does not need to go to the modem,
just to the phone line. That is fairly easy to accomplish,
either using the modem, or not.

>I'll only look at the second as it makes the first pretty much moot.
>
>Modems are DTE devices -- _data_ terminal equipment.
>
>Modems (_mo_dulator/_dem_odulator) use the analog _circuit_ facilities
>of the POTS (ie., PSTN) to make a connection to another DTE at the far
>end -- phones are not DTE's.


Well, yeah, but that isn't significant.

>Two modems connected to each other via POTS use a terminal emulator
>for human use. Thus all the terminal emulation options available in
>modem software packages.


Eh?

>Modems can also be used to dial into a network (connecting to another
>DTE device) and have that far end "plug" you into the network. This
>is normally done with PPP -- point-to-point protocol. PPP is a


Eh?

>"generalized" protocol that can carry (encapsulate/frame) many link
>layer protocols. That's why you see things like PPPoE and PPPoATM.
>We won't go into the details of wire signaling, etc.


You've got that backwards. The little 'o' indicates that the
PPP is being carried (encapsulated) by the 'E' or the 'ATM', not
the other way around.

>Point is that a modem is a (digital) _data_ device, not an analog
>transmitter despite the fact that it uses the analog (voice) circuit
>facilities of the "phone company".


A modem is in fact *both* a digital device and an analog
"transmitter".

>The voice _facilities_ of the phone companies would be available with
>an interface card that speaks FSO/FXO.


That is totally bogus too. FXS/FXO merely means that instead of
connecting a wire line loop to an interface designed for a
wireline loop, there is a non-wireline carrier system in
between. The FXS provides an interface to the real wireline
loop (e.g., a telephone set) and the FXO provides what looks
like a wireline loop to the interface (e.g., a line card in a
telephone switch). The carrier facility in between can be
almost anything (fiber, microwave, digital carrier, analog
carrier, whatever).

> Acquiring something as mundane
>as a dial tone is not s easy as you might think. No need to go into


Oh, come on. It requires all of providing a DC path on the
loop. You can get a dialtone by shorting the cable pairs! You
just can't hear it when you do that...

>boring details (and their many variations) -- just know that modems
>cannot utilize analog _voice_ facilities.


Bullshit. That is exactly what they are designed to do. And
it's been a *long* time since the dialer (ACU) and the
modulator/demodulator portions of a modem were separate units.

>Faxes are another hardware interface that uses the _circuit_
>facilities of POTS. Faxes _pre-date_ computers -- sometime in the
>1930's IIRC and using the grandfarther of today's hi-res drum
>scanners. That's why the term "fax/modem" -- a modem is not a fax
>interface device without extra hardware.


A fax includes a modem. A modem isn't a "FAX" until you add
a printer...

>"Voice" modems have minimal ability to process a voice signal --
>namely record or playback a "voice stream". With software they can be
>used to build suprisingly sophisticated (and large) voice mail
>systems. In both cases this is a dial-in capability -- not dial-out.
>Well, not entirely true, as these modems could be used for messaging
>services, like _sending_ pager text.


I'm not really familiar with voice modems, as I've never owned
or used one. But what you just said is in effect that a voice
modem will do *exactly* what the OP wants!

>For all this, modems still cannot establish and carry on a full duplex
>_voice_ connection like a simple handset! But then they weren't
>designed to do so.


I don't see why not! As I said, I've never used a voice modem,
so I'm not sure they actually have the ability to do what you
described above. But if they do, then clearly they can carry on
a full duplex voice connection. (Incidentally, a "simple
handset" cannot! It requires a slightly more complex "telset",
which means there has to be a hybrid network in order to have
full duplex.)

>If what you propose were possible, you would be able to sit at the
>Linux box, strap on a mic'ed headset, and dial your neighbor who picks
>up their phone handset, and chatter away. Ever picked up your handset
>when a modem is at the other end "calling"?


I see no reason at all that you cannot arrange to dial your
neighbor and chatter away. The modem doesn't necessarily *have*
to produce carrier tones! In fact, you might notice that it
dials up a connection and if you tell the modem to dial your
neighbor and pick up your an extension line, you can talk to the
neighbor just fine and the modem will not make a peep.

>I've taken liberties and shortcuts galore, but hopefully you have some
>sense of _why_ your setup will not work -- the idea is OK but the
>hardware is against you


If the "voice modem" has the ability to send and receive audio
over the phone line (which means the modem must have both an
input and an output jack for audio), then it is definitely
possible to control the modem via the rs-232 connection and use
the computer's sound card(s) for the audio interface. Note too
that if the modem cannot do that, it is technically blindingly
simple to provide that functionality (it is basically the same
thing as a "phone patch" used by CB or Ham operators). The
modem can be used for dialing and for hook-switch control.

A sound card that will work full duplex is also necessary, and
of course there is the little matter of software to control all
of this.

Of course, when all of this is put together what it amounts to
is an expensive, hard to maintain, piece of junk. And it is
going to _sound_ exactly like what it is...

--
FloydL. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) (E-Mail Removed)
 
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P Gentry
Guest
Posts: n/a
 
      09-10-2004
(E-Mail Removed) (Floyd L. Davidson) wrote in message news:<(E-Mail Removed)>...
> (E-Mail Removed) (P Gentry) wrote:
> >"C3" <_> wrote in message news:<41404ae0$0$3710$(E-Mail Removed) u>...
> >> > Connect to Linux box via internet and have that Linux box provide a
> >> > dial tone so that the internet conncected host can then place a
> >> > "standard" PSTN voice call?
> >>
> >> That's correct.
> >>

> >[snip]
> >


Arghhhh -- Floyd D. saw me blathering in public. Was afraid of that


> >OK. Two problems:
> >a) how to "pipe" the sound card's output to the modem
> >b) how will the modem "transmit" this output to a _phone_

>
> The sound card's output does not need to go to the modem,
> just to the phone line. That is fairly easy to accomplish,
> either using the modem, or not.


I'll give you my phone # if you think it's that easy

> >I'll only look at the second as it makes the first pretty much moot.
> >
> >Modems are DTE devices -- _data_ terminal equipment.
> >
> >Modems (_mo_dulator/_dem_odulator) use the analog _circuit_ facilities
> >of the POTS (ie., PSTN) to make a connection to another DTE at the far
> >end -- phones are not DTE's.

>
> Well, yeah, but that isn't significant.


Just what, pray tell, will the modem "talk" to at the other end then?
A modem modualtes/demodulates the "audio" signal into a byte stream.
That's why they require settings like 8NP or 7NP or 7+P (# of
bits/parity)

> >Two modems connected to each other via POTS use a terminal emulator
> >for human use. Thus all the terminal emulation options available in
> >modem software packages.

>
> Eh?


Surely you're kidding. Dial-in BBSes, VT100 and ANSI terminal menus,
command sets, and keyboard layouts -- mostly of historical interest
perhaps? Modems are a _byte_ stream _digital_ device -- and
asynchronous at that. In this context, think telnet.

> >Modems can also be used to dial into a network (connecting to another
> >DTE device) and have that far end "plug" you into the network. This
> >is normally done with PPP -- point-to-point protocol. PPP is a

>
> Eh?


RADIUS? AOL? MSN? Huh?

> >"generalized" protocol that can carry (encapsulate/frame) many link
> >layer protocols. That's why you see things like PPPoE and PPPoATM.
> >We won't go into the details of wire signaling, etc.

>
> You've got that backwards. The little 'o' indicates that the
> PPP is being carried (encapsulated) by the 'E' or the 'ATM', not
> the other way around.


Yeah, noticed that 5 mins _afterwards_ -- got interupted and the the
old brain cells were slow to kick in with, "Duh!". Figured someone
might catch it.

> >Point is that a modem is a (digital) _data_ device, not an analog
> >transmitter despite the fact that it uses the analog (voice) circuit
> >facilities of the "phone company".

>
> A modem is in fact *both* a digital device and an analog
> "transmitter".


Yes, that's why they are called mo-dems, but they have no ability to
transmit an _un_modulated voice signal. The mo and the dem is how
they "encode" and "decode" the digital bits.

> >The voice _facilities_ of the phone companies would be available with
> >an interface card that speaks FSO/FXO.

>
> That is totally bogus too. FXS/FXO merely means that instead of
> connecting a wire line loop to an interface designed for a
> wireline loop, there is a non-wireline carrier system in
> between. The FXS provides an interface to the real wireline
> loop (e.g., a telephone set) and the FXO provides what looks
> like a wireline loop to the interface (e.g., a line card in a
> telephone switch). The carrier facility in between can be
> almost anything (fiber, microwave, digital carrier, analog
> carrier, whatever).


Was only included to indicate the "reality" that a FXS/FXO capable
card is the only reasonable ($) hope of carrying on a "relayed"
connection. Plus these are the kind of cards OP will most likely see
referenced. Have not kept up over the past 5 years, so if you know of
something better I would be interested to hear about it. A link?

> > Acquiring something as mundane
> >as a dial tone is not s easy as you might think. No need to go into

>
> Oh, come on. It requires all of providing a DC path on the
> loop. You can get a dialtone by shorting the cable pairs! You
> just can't hear it when you do that...


"dial tone" in the sense that we think of a handset dial tone -- but
you're _right_, I should not have injected this as it doesn't further
anything.

> >boring details (and their many variations) -- just know that modems
> >cannot utilize analog _voice_ facilities.

>
> Bullshit. That is exactly what they are designed to do. And
> it's been a *long* time since the dialer (ACU) and the
> modulator/demodulator portions of a modem were separate units.


Splitting tech (short)hairs -- and who said _anything_ about any kind
of separate units. (Though I did toy with the idea of "remembering"
the first modems that were cradles _for_ a handset!)

If you can come up with a better phrase to indicate what the average
joe thinks of when when speaking about "voice" and "phones" I'm more
than willing to accept -- never cared for this (my) phrase used here,
but wasn't going to spend more than ten mins thinking of a better
expression. Just call me slow witted BTW, don't try your method
with a trunked PBX -- they acquire dial tones in a differnet manner.

> >Faxes are another hardware interface that uses the _circuit_
> >facilities of POTS. Faxes _pre-date_ computers -- sometime in the
> >1930's IIRC and using the grandfarther of today's hi-res drum
> >scanners. That's why the term "fax/modem" -- a modem is not a fax
> >interface device without extra hardware.

>
> A fax includes a modem. A modem isn't a "FAX" until you add
> a printer...


Well, here I'll say quite definitively that you are simply too "wired
into" current technology packages and that about faxes and fax
machines (old and current) you have this "backwards" -- have installed
100's of fax machines _and_ cards that were modem-less. They are
different technologies both using the "phone lines". Neither one
_requires_ the other, despite their "similar" use of the phone lines.
They _can_ share certain abilities/requirements, like acquiring a dial
tone For establishing a session and transmitting data they are
completely different.

> >"Voice" modems have minimal ability to process a voice signal --
> >namely record or playback a "voice stream". With software they can be
> >used to build suprisingly sophisticated (and large) voice mail
> >systems. In both cases this is a dial-in capability -- not dial-out.
> >Well, not entirely true, as these modems could be used for messaging
> >services, like _sending_ pager text.

>
> I'm not really familiar with voice modems, as I've never owned
> or used one. But what you just said is in effect that a voice
> modem will do *exactly* what the OP wants!


One would think so. The dial-in capability (voice mail) requires
_both_ hardware _and_ software additions to a basic modem -- and if
"extended" you might think this would allow a modem to act as a
handset. (Not sure why this was never carried out -- technical, $,
regulations, opposition, public acceptance?) The dial-out capability
was a means of "plugging into" services provided by the phone company.
Without the CO facilities it would not work -- nothing to work with.

> >For all this, modems still cannot establish and carry on a full duplex
> >_voice_ connection like a simple handset! But then they weren't
> >designed to do so.

>
> I don't see why not! As I said, I've never used a voice modem,
> so I'm not sure they actually have the ability to do what you
> described above. But if they do, then clearly they can carry on
> a full duplex voice connection. (Incidentally, a "simple
> handset" cannot! It requires a slightly more complex "telset",
> which means there has to be a hybrid network in order to have
> full duplex.)


You misunderstand "handset" -- I'm speaking of the RJ11 connected
phone most "hard wired" phone users pick up to dial out or answer a
call.

> >If what you propose were possible, you would be able to sit at the
> >Linux box, strap on a mic'ed headset, and dial your neighbor who picks
> >up their phone handset, and chatter away. Ever picked up your handset
> >when a modem is at the other end "calling"?

>
> I see no reason at all that you cannot arrange to dial your
> neighbor and chatter away. The modem doesn't necessarily *have*
> to produce carrier tones! In fact, you might notice that it
> dials up a connection and if you tell the modem to dial your
> neighbor and pick up your an extension line, you can talk to the
> neighbor just fine and the modem will not make a peep.


You _have_ to pick up your "handset" to chatter away _because_ a modem
can't provide that capability. In fact, early modems wouldn't even
allow you to "interrupt" a modem session (they wouldn't "release")
this way. Last time I actually used this "method" of dialing out, you
also had to pick up the handset within a limited amount of time. And
it won't work with most (any?) modems without a pass-through jack.

> >I've taken liberties and shortcuts galore, but hopefully you have some
> >sense of _why_ your setup will not work -- the idea is OK but the
> >hardware is against you

>
> If the "voice modem" has the ability to send and receive audio
> over the phone line (which means the modem must have both an
> input and an output jack for audio), ...


Nope, it "looks" like just a regular plug-in or serial modem -- no
separate "audio" cords -- though some provide external jacks and some
require/use your sound card. When someone calls in to _leave_ a voice
mail, the handset they are using is effectivey the "mic" -- in fact,
many "voice modems" require you to use the pass-through handset as a
mic to record "intro" or "direction" messages for the voice mail
system. (All the ones that I used on-site were this way.)

> ... then it is definitely
> possible to control the modem via the rs-232 connection and use
> the computer's sound card(s) for the audio interface.


This was (is) done sometimes to a limited extent but due to the
proprietary nature of most (all?) sound cards at the time (circa
'93-95) it was "less that reliable".

> ... Note too
> that if the modem cannot do that, it is technically blindingly
> simple to provide that functionality (it is basically the same
> thing as a "phone patch" used by CB or Ham operators). ...


And as above, I'm not sure why it was never followed up.

> ... The modem can be used for dialing and for hook-switch control.


Unfortunately, that's about all a modem can be used for at this level.
Beyond this and the byte stream encoding/decoding (mo - dem) starts
up.

> A sound card that will work full duplex is also necessary, and
> of course there is the little matter of software to control all
> of this.
>
> Of course, when all of this is put together what it amounts to
> is an expensive, hard to maintain, piece of junk. And it is
> going to _sound_ exactly like what it is...


Which is why I suggested that OP look at providers that offer internet
VoIP services or internet phone services -- whichever he is most
interested in.

BTW, I hope the folks around here that need some RS232 advice (among
other things) know what a resource you provide. I did _one_ measly
and "easy" project collecting data from a bar code scanner that
downloaded library spine codes. On top of that, you regularly watch
the posts and provide accurate help.

regards,
prg
email above disabled
 
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David M
Guest
Posts: n/a
 
      09-12-2004

>Yes, that's why they are called mo-dems, but they have no ability to
>transmit an _un_modulated voice signal. The mo and the dem is how
>they "encode" and "decode" the digital bits.
>
>> >The voice _facilities_ of the phone companies would be available with
>> >an interface card that speaks FSO/FXO.

>>
>> That is totally bogus too. FXS/FXO merely means that instead of
>> connecting a wire line loop to an interface designed for a
>> wireline loop, there is a non-wireline carrier system in
>> between. The FXS provides an interface to the real wireline
>> loop (e.g., a telephone set) and the FXO provides what looks
>> like a wireline loop to the interface (e.g., a line card in a
>> telephone switch). The carrier facility in between can be
>> almost anything (fiber, microwave, digital carrier, analog
>> carrier, whatever).

>
>Was only included to indicate the "reality" that a FXS/FXO capable
>card is the only reasonable ($) hope of carrying on a "relayed"
>connection. Plus these are the kind of cards OP will most likely see
>referenced. Have not kept up over the past 5 years, so if you know of
>something better I would be interested to hear about it. A link?



Hi,

I was wondering with this discussion how a "Winmodem"/ AMR Card might work
as I have heard them disparagingly called a limited soundcard.

Iff you have access to an ADC/DAC pair in a soundcard type configuration
there should not be a problem with voice.

(If not don't the whole point is moot as well as if the ADC/DAC doesn't have
enough bits..)

The advantage of one of these cards should offer all the needs to connect to
a line. (Voltage isolation, line pickup etc. and although a permitted
attachment they probably don't have permission as a phone..)

The only disadvantage is that there is no software written for using this
type of card as a telephone interface.




--

Regards,

David
 
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Marc H.Popek
Guest
Posts: n/a
 
      09-12-2004
Here is some hardware to facilitate the switch between the voip router and
the plain old telephone service!

http://cgi.ebay.com/ws/eBayISAPI.dll...7379&ssPageNam
e=STRK:MESE:IT

or wireless wi fi links


http://cgi.ebay.com/ws/eBayISAPI.dll...1404&ssPageNam
e=STRK:MESE:IT



"Marc H.Popek" <(E-Mail Removed)> wrote in message news:...
> Here is an excerpt of an amazing device that solves a long standing

problem
> with VOIP. you get a great long distance rate but no local telephone
> presence... so you add a local phone and now you have a dis-joined system.
> what to do?
>
> Use combine-a-line to automatically switch and join your voip and your

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>
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>
>

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> e=STRK:MESE:IT
>
>
>
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>
>
>
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> ID or PC Modem on TWO phone lines?.. Automatically?
>
>
>
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> PROTECTION INSIDE) your communications for your home office or for the
> family.
>
>
>
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switch
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>
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http://cgi.ebay.com/ws/eBayISAPI.dll...1404&ssPageNam
e=STRK:MESE:IT
"C3" <_> wrote in message
news:413d53ba$0$32424$(E-Mail Removed) u...
> Hello. I would like to set up a linux box connected to a phone line so

that
> I can connect to it over the internet and receive a dial-tone as though i
> had picked up the phone where the linux machine is.
>
> In theory, this seems very simple to do. Once authenticated, the linux box
> issues a couple of commands to the modem, starts recording from the modem
> and sending that data, and also passing the incoming voice data to the

phone
> line.
>
> I don't want to have to run some huge VoIP software package. Ideally, this
> sort of thing can be achieved in a very lightweight fashion.
>
>
> Comments please.
>
>



---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.726 / Virus Database: 481 - Release Date: 7/22/2004


 
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Floyd L. Davidson
Guest
Posts: n/a
 
      09-12-2004
(E-Mail Removed) (P Gentry) wrote:
>(E-Mail Removed) (Floyd L. Davidson) wrote:
>>
>> The sound card's output does not need to go to the modem,
>> just to the phone line. That is fairly easy to accomplish,
>> either using the modem, or not.

>
>I'll give you my phone # if you think it's that easy


Really, it is. Every sound card has a "line in" and a "line
out" jack. You want that to go to a telephone line? Put any
standard telephone hybrid network between the sound card and the
telephone line! Every phone patch, telephone set, modem,
etc. etc. has such a network in it. (The network from a
telephone set won't work though, only because it has a
"sidetone" path that is great for a telset, but bad for this
application.)

>> >Modems (_mo_dulator/_dem_odulator) use the analog _circuit_ facilities
>> >of the POTS (ie., PSTN) to make a connection to another DTE at the far
>> >end -- phones are not DTE's.

>>
>> Well, yeah, but that isn't significant.

>
>Just what, pray tell, will the modem "talk" to at the other end then?
>A modem modualtes/demodulates the "audio" signal into a byte stream.
>That's why they require settings like 8NP or 7NP or 7+P (# of
>bits/parity)


The modem need not talk to anything. It will quietly sit there
doing nothing if you don't enable the transmitter. The usual
configuration is that one modem is in "originate mode", which
does *not* send tones until triggered by reception of tones.
The other modem is in "answer mode", which immediately does send
tones. As long as the modem being used is in originate mode
there will be no tones unless you dial up a modem that is in
answer mode.

>> >Two modems connected to each other via POTS use a terminal emulator
>> >for human use. Thus all the terminal emulation options available in
>> >modem software packages.

>>
>> Eh?

>
>Surely you're kidding. Dial-in BBSes, VT100 and ANSI terminal menus,
>command sets, and keyboard layouts -- mostly of historical interest
>perhaps? Modems are a _byte_ stream _digital_ device -- and
>asynchronous at that. In this context, think telnet.


The first sentence of the original statement is wrong. It
flatly says that *all* modems connected via POTs for human use
necessarily use a terminal emulator. That is simply not true.
I've written dozens of small serial port programs that connect
two modems via POTS and talk to some remote device (everything
from telco Channel Banks to remote temperature sensing devices).
Most of those uses do *not* involve a terminal emulator.

Your followup isn't too great either! Modems are not "byte
stream" devices, nor are they asynchronous. The interface to
the computer is both of those; but the communications between
modems is almost always (as in, I don't know of a single modem
that is not) a bit oriented data stream. With v.32 and v.90 it
is synchronous too. (Actually, even Bell 103 modems are
synchronous at the modem to modem level, but they are not
packetized so that distinction is meaningless.)

>> >Modems can also be used to dial into a network (connecting to another
>> >DTE device) and have that far end "plug" you into the network. This
>> >is normally done with PPP -- point-to-point protocol. PPP is a

>>
>> Eh?

>
>RADIUS? AOL? MSN? Huh?


You should say "often", not "normally". Perhaps the use you are
familiar with is normally just that. Others may normally see
something very different...

....

>> >Point is that a modem is a (digital) _data_ device, not an analog
>> >transmitter despite the fact that it uses the analog (voice) circuit
>> >facilities of the "phone company".

>>
>> A modem is in fact *both* a digital device and an analog
>> "transmitter".

>
>Yes, that's why they are called mo-dems, but they have no ability to
>transmit an _un_modulated voice signal. The mo and the dem is how
>they "encode" and "decode" the digital bits.


A modem today is not solely a modulator and a demodulator. Most
modems include a pretty serious bit of computational capability,
not to mention signal processing. Some of them even seem to have
the ability to transmit "an _un_modulated voice signal"!

The simple "modulator/demodulator" was actually called a
"terminal unit", and the telephone industry used them to
multiplex Teletype channels onto a carrier voice channel. (A
43A1 TU used about 5 tubes if I remember right, would run at
speeds up to 75 baud, and could be stacked with as many as 16 to
a single voice channel because it used 180 Hz FSK!)

(Speaking of making modems do things the manufacture never meant
them to... I used to use 43A1 Terminal Units as a tube tester!
They used WECO 408 tubes, as did many other pieces of equipment,
X type SF signaling units being one example. But the SF Unit
didn't need a particularly high gain 408 tube, and the 43A1 did.
So I set up a row of about 48 sockets with the only filaments
wired up, and would plug 4 dozen tubes in and let them burn in
for a few days to stablize them. Then I'd take them one at a
time an plug them into a spare 43A1, with an AC VTVM probe on
the output pin jack. Tube went back into boxes, sorted by which
would be used for SF Units, other equipment, or 43A1's. Low
gain, medium gain, and high gain... Eventually that was no
longer necessary because WECO started doing essentially the same
thing, and sold a 408A/B tube specifically for the 43A1 units.)

Whatever, when "modem" concept first moved to the customer
location the speed and bandwidth were slightly increased (135
baud!), and an external dialing unit was required. But shortly
the two were combined, and a "modem" as we know them was born...
and has *never* since then been restricted to just a modulator
and a demodulator.

A modern modem can probably handle voice. It can also do a
significant bit of digital signal processing (of the analog
signal) because every v.32, v.34, v.90 or v.92 modem contains a
digital echo cancellor. A pretty fancy little device, actually.

>> >The voice _facilities_ of the phone companies would be available with
>> >an interface card that speaks FSO/FXO.

>>
>> That is totally bogus too. FXS/FXO merely means that instead of
>> connecting a wire line loop to an interface designed for a
>> wireline loop, there is a non-wireline carrier system in
>> between. The FXS provides an interface to the real wireline
>> loop (e.g., a telephone set) and the FXO provides what looks
>> like a wireline loop to the interface (e.g., a line card in a
>> telephone switch). The carrier facility in between can be
>> almost anything (fiber, microwave, digital carrier, analog
>> carrier, whatever).

>
>Was only included to indicate the "reality" that a FXS/FXO capable
>card is the only reasonable ($) hope of carrying on a "relayed"
>connection.


That just is not true. An FXS/FXO setup is merely one particular
type of "relayed" connection. It doesn't specifically apply to
the OP's scenario because the OP has no need to convert a wireline
loop interface into something that will emulate one for the distant
end.

There is some similarity though, and if you remove the "only
reasonable" bit, it does make a good example of what is needed:

2-wire 4-wire 2-wire
+-----+ wireline +-----+ carrier +-----+ wireline +--------+
| Tel | loop | |--->>>---| | loop | telco |
| Set |-----//---| FXS | | FXO |----//----| switch |
| | | |---<<<---| | | |
+-----+ +-----+ +-----+ +--------+

The reason for this is because the "4-wire carrier" cannot
transmit DC pulses or loop current. It might be a microwave or
a fiber optic system, for example, and the telset may be located
hundreds of miles from the telco switch. So the DC pulses and
loop current are converted to some other form of signaling.
With analog systems it was almost always SF (2600 Hz "Single
Frequency"). With digital systems it almost always uses Robbed
Bit Signaling (the AB bits in a the SuperFrame of a DS1 rate
digital line).

The similarity with the OP's scenario is that if we chop off the
entire left hand side, and provide something like this,

4-wire 2-wire
+------------+ +-----+ wireline +--------+
| computer |---->>>----| | loop | telco |
| voice card | | FXO |----//----| switch |
| |----<<<----| | | |
+------------+ +-----+ +--------+

We have the same thing, except the computer has to synthesize
whatever it is that the FXO expects to see on it's 4-wire voice
channel side for signaling and supervision. That isn't
technically difficult, and there no doubt are off the self units
where the FXO card plugs right into a PCI slot in the computer.

However, another way to to it is to use out of band signaling,
and a voice modem,

4-wire 2-wire
+------------+ +-----+ wireline +--------+
| computer |---->>>----| | loop | telco |
| voice card | |modem|----//----| switch |
| |----<<<----| | | |
+------------+ +-----+ +--------+
| |
| RS-232 supervision |
+---------------------+

That might seem odd to some, but consider this very common
telco equipment configuration for a FXS/FXO,

2-wire 4-wire 4-wire
+-----+ wireline +-----+ carrier +-----+ trunk +--------+
| Tel | loop | |--->>>---| |----->>>----| telco |
| Set |-----//---| FXS | | FXO | | switch |
| | | |---<<<---| |-----<<<----| |
+-----+ +-----+ +-----+ +--------+
| |
| E&M DC Supervision |
+--------------------+

The difference is that the telco interfaces to a 4-wire _trunk_
card rather than to a 2-wire _line_ card.

Clearly the OP can make a choice between in-band and out-of-band
signaling, and that amounts to choosing which hardware to buy.

>Plus these are the kind of cards OP will most likely see
>referenced. Have not kept up over the past 5 years, so if you know of
>something better I would be interested to hear about it. A link?


I'm sure a search on google would turn up a list of interesting
links. It is also possible that posting a query to
comp.dcom.modems and crossposting it to alt.dcom.telecom and
comp.dcom.telecom.tech might be productive.


>> >boring details (and their many variations) -- just know that modems
>> >cannot utilize analog _voice_ facilities.

>>
>> Bullshit. That is exactly what they are designed to do. And
>> it's been a *long* time since the dialer (ACU) and the
>> modulator/demodulator portions of a modem were separate units.

>
>Splitting tech (short)hairs -- and who said _anything_ about any kind
>of separate units. (Though I did toy with the idea of "remembering"
>the first modems that were cradles _for_ a handset!)


See the above discussion.

>If you can come up with a better phrase to indicate what the average
>joe thinks of when when speaking about "voice" and "phones" I'm more
>than willing to accept -- never cared for this (my) phrase used here,
>but wasn't going to spend more than ten mins thinking of a better


Perhaps, but that is not the point. The point is that the modem has
both mod/demod capability *and* supervision capability. Using only
the supervision capability isn't exactly unheard of.

>expression. Just call me slow witted BTW, don't try your method
>with a trunked PBX -- they acquire dial tones in a differnet manner.


Oh, whoop dee do. Some (but not all) PBX's use "ground start"
rather than "loop start" on wireline trunks. Big deal. We
aren't talking about ground start lines (and there *are* both
telephones and modems that can use ground start too). Moreover,
in addition to those two interfaces which are commonly used for
lines, there is the myriad list of trunk interfaces too, which
many PBX's also use. Who cares, since that was not what the OP
specified, nor is it necessary for the OP to even consider
anything other than interfacing to a standard POTS line (unless
of course he arbitrarily wants to).

>> >Faxes are another hardware interface that uses the _circuit_
>> >facilities of POTS. Faxes _pre-date_ computers -- sometime in the
>> >1930's IIRC and using the grandfarther of today's hi-res drum
>> >scanners. That's why the term "fax/modem" -- a modem is not a fax
>> >interface device without extra hardware.

>>
>> A fax includes a modem. A modem isn't a "FAX" until you add
>> a printer...

>
>Well, here I'll say quite definitively that you are simply too "wired
>into" current technology packages and that about faxes and fax
>machines (old and current) you have this "backwards" -- have installed
>100's of fax machines _and_ cards that were modem-less.


You have *never* installed a fax machine that did not have a modem
in it!

>They are
>different technologies both using the "phone lines". Neither one
>_requires_ the other, despite their "similar" use of the phone lines.


That is absolutely wrong. *Every* FAX by definition has a modem
as an essential part, by definition. That modem may not use
v.32, v.34, v.90, or v.92 modem protocols, but then again it
might not use v.26, v.27 v.29 or v.33 modem protocols either
(and neither would the modem *you* use). Regardless, those are
all "modem protocols", and FAX modems, for example, use v.29
modem protocols for 4800, 7200, and 9600 bps transmissions.
FAX modems might also use v.17, v.27 or v.34 modem protocols.

>They _can_ share certain abilities/requirements, like acquiring a dial
>tone For establishing a session and transmitting data they are
>completely different.


Bullshit. FAX machines use a modem to 1) acquire a dial tone,
2) establish a session, and 3) transmit data. That might even
be done with *exactly* the same hardware and modem protocol
(v.34) that is used for computer data. In fact, any high speed
FAX machine that works at a speed greater than 14.4Kbps is going
to use v.34 protocols. The slower protocols are still more
common, but they are different only in detail, not in
functionality or overall purpose from the various modem
protocols used for computer data.

>> >"Voice" modems have minimal ability to process a voice signal --
>> >namely record or playback a "voice stream". With software they can be
>> >used to build suprisingly sophisticated (and large) voice mail
>> >systems. In both cases this is a dial-in capability -- not dial-out.
>> >Well, not entirely true, as these modems could be used for messaging
>> >services, like _sending_ pager text.

>>
>> I'm not really familiar with voice modems, as I've never owned
>> or used one. But what you just said is in effect that a voice
>> modem will do *exactly* what the OP wants!

>
>One would think so. The dial-in capability (voice mail) requires
>_both_ hardware _and_ software additions to a basic modem -- and if
>"extended" you might think this would allow a modem to act as a
>handset. (Not sure why this was never carried out -- technical, $,
>regulations, opposition, public acceptance?) The dial-out capability
>was a means of "plugging into" services provided by the phone company.
> Without the CO facilities it would not work -- nothing to work with.


Well, gee... a POTS line that won't work without a CO is not exactly
a revelation! Your regular telephone set requires that too!

I'm not sure what the significance is that it requires more
software and hardware than just a modem. So what? Computer
data transfer requires more software too. It also requires
significant hardware, and the only difference is that the
hardware required is so universally needed that it is provided
by default. But a serial port is *not* necessary for a computer
to function otherwise...

>> >For all this, modems still cannot establish and carry on a full duplex
>> >_voice_ connection like a simple handset! But then they weren't
>> >designed to do so.

>>
>> I don't see why not! As I said, I've never used a voice modem,
>> so I'm not sure they actually have the ability to do what you
>> described above. But if they do, then clearly they can carry on
>> a full duplex voice connection. (Incidentally, a "simple
>> handset" cannot! It requires a slightly more complex "telset",
>> which means there has to be a hybrid network in order to have
>> full duplex.)

>
>You misunderstand "handset" -- I'm speaking of the RJ11 connected
>phone most "hard wired" phone users pick up to dial out or answer a
>call.


A handset plugs into a telset. The telset (not a handset) plugs
into the telephone line.

Typical residential users rarely see either a handset or a
telset without seeing the other, and since the introduction of
the "Princess" telephone way back when it is not uncommon (e.g.,
cell phones) to see the two devices combined as a single unit.

However, they are in fact two very separate items. Commonly the
handset on many telsets has a cord that can be replaced (with a
longer one, for example). But in some places you'll find the
two are *very* distinct. Operator switchboards, for example.
Each operator has a *personal* handset, that nobody else ever
uses. They sit down and plug it into a telset, which is perhaps
one of several, but all of them would commonly be used by
whoever happens to be physically where that telset is located.

Your misuse of the terminology is not a reflection on my
understanding of it...

>> I see no reason at all that you cannot arrange to dial your
>> neighbor and chatter away. The modem doesn't necessarily *have*
>> to produce carrier tones! In fact, you might notice that it
>> dials up a connection and if you tell the modem to dial your
>> neighbor and pick up your an extension line, you can talk to the
>> neighbor just fine and the modem will not make a peep.

>
>You _have_ to pick up your "handset" to chatter away _because_ a modem
>can't provide that capability. In fact, early modems wouldn't even


That is simply not true. Voice modems provide exactly that
functionality.

>allow you to "interrupt" a modem session (they wouldn't "release")
>this way. Last time I actually used this "method" of dialing out, you
>also had to pick up the handset within a limited amount of time. And
>it won't work with most (any?) modems without a pass-through jack.


But *clearly* you are being limited by your ability to configure
the software. The hardware is quite capable of doing exactly as
described, and there is a myriad of software available to use
that functionality in a variety of ways.

>> If the "voice modem" has the ability to send and receive audio
>> over the phone line (which means the modem must have both an
>> input and an output jack for audio), ...

>
>Nope, it "looks" like just a regular plug-in or serial modem -- no
>separate "audio" cords -- though some provide external jacks and some
>require/use your sound card. When someone calls in to _leave_ a voice
>mail, the handset they are using is effectivey the "mic" -- in fact,
>many "voice modems" require you to use the pass-through handset as a
>mic to record "intro" or "direction" messages for the voice mail
>system. (All the ones that I used on-site were this way.)


You are contradicting yourself. A non-voice modem does not
connect to the sound card. A "voice modem" does, and uses the
"some provide external jacks and some require/use your sound
card" functionality. If someone calls to leave a message, the
audio is passed from the telephone line to the sound card input,
and the sound card converts it to PCM or whatever type of
digital encoding and stores it on disk. The outgoing message to
the calling party was previously stored on disk, and the sound
card converts it from PCM, or whatever, and outputs that on the
"line out" jack that connects to the "line in" on the modem and
that is sent to the telephone line.

Precisely what the OP wants to do, except he wants real time
digital i/o rather than using store and forward audio from a
disk file.

>> ... then it is definitely
>> possible to control the modem via the rs-232 connection and use
>> the computer's sound card(s) for the audio interface.

>
>This was (is) done sometimes to a limited extent but due to the
>proprietary nature of most (all?) sound cards at the time (circa
>'93-95) it was "less that reliable".


Eh? You've been saying it can't be done, and now point out that
it has been being done for a decade. And I won't agree at all
with the idea that is was seriously limited by the '93-95 time
frame, though I'd say that was indeed true a decade before that.
Of course, we are talking about a technology that has been
commercially available for 20 years now! It may not be fully
mature, but this isn't exactly bleeding edge stuff any more!

>> ... Note too
>> that if the modem cannot do that, it is technically blindingly
>> simple to provide that functionality (it is basically the same
>> thing as a "phone patch" used by CB or Ham operators). ...

>
>And as above, I'm not sure why it was never followed up.


Lots of call centers use exactly that functionality, so it
really isn't correct to say it was never followed up on. It
just doesn't have much use in the consumer modem market, that's
all.

>> ... The modem can be used for dialing and for hook-switch control.

>
>Unfortunately, that's about all a modem can be used for at this level.
> Beyond this and the byte stream encoding/decoding (mo - dem) starts
>up.


No it doesn't. There is no requirement that the modulator be
enabled at all.

And supervision is not the only potential use either. Virtually
every modem contains a very significant capability for digital
signal processing, and every one of them implements an echo
cancellor. That has benefits for voice calls too. Likewise it
would take very little additional programming to allow the modem
to do just about anything you'd like to the telephone line (from
test signals to voice recognition). All that's needed is a
*reason* for someone to add extra functionality to the modem.
In many cases it would require no extra hardware, and could be
added by merely flashing the modem's memory.

>> Of course, when all of this is put together what it amounts to
>> is an expensive, hard to maintain, piece of junk. And it is
>> going to _sound_ exactly like what it is...

>
>Which is why I suggested that OP look at providers that offer internet
>VoIP services or internet phone services -- whichever he is most
>interested in.


I don't see much difference... VoIP hasn't quite gotten to the
point where it is much more than "an expensive, hard to
maintain, piece of junk" itself! However, it is right on the
verge... and when it really does arrive it *will* cause an
entire paradigm shift that will forever change the telecom voice
message business.

>BTW, I hope the folks around here that need some RS232 advice (among
>other things) know what a resource you provide. I did _one_ measly
>and "easy" project collecting data from a bar code scanner that
>downloaded library spine codes. On top of that, you regularly watch
>the posts and provide accurate help.


You sure make it hard to pick on you. If you'd just be a
"normal" Usenet guy, and snarl a little, we could call each
other names and all kinds of things, eh?

(And I really do appreciate that you are NOT a "normal Usenet
guy"! And while you may be saying a few things that are quite
technically correct, that is of little significance compared to
the interesting information that the resulting discussion
produces. I may know a bunch of technical details, but you are
the one with enough imagination to make this all interesting!)

--
FloydL. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) (E-Mail Removed)
 
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P Gentry
Guest
Posts: n/a
 
      09-13-2004
"C3" <_> wrote in message news:<4140e475$0$30576$(E-Mail Removed). au>...
> The only news to me is that voice modems are not capable of performing the
> very limited task needed of them.


Depends on what you mean by "limited". The "voice" in voice modems
refers to the dsp and codec firmware that _digitizes_ the analog voice
stream (and vice versa). It's the software that actually provides
what we, as users, think of as the functionality. Ie., voice mail,
answering machine, video phone (haven't seen one of those in a while),
etc. Voice mail and fax are probobaly the two most used "extras"
beyond simple data linking for dial-up networking.

> I always believed that voice modems are simply modems that can receive a
> signal through a 3.5" minijack and pass it onto the phone line, and also to
> send out the sound from the phoneline onto another 3.5" minijack plug. These
> two can be connected to the input and output of a soundcard.


"Everyone" (me too) has tried this at one time or other -- these lines
(sound card to modem) won't "match" for one thing and the other
problem is that the input/mic jack on the modem is just to _record_ a
message. Obviates the need for a separate sound card for input _or_ a
"speakerphone" (mic and speackers). A person-in-the-flesh doesn't
really need a modem to "speak" on the wire -- that's what POTS and
handsets are for.

> The only thing left is to dial the number, that's just an ATDT away, isn't
> it?


All modems _can_ dial out. The problem is that without human
intervention (lifting up the handset, eg.) or some software app the
modem will try to contact another _data_ modem. If you lift the
handset before the modem/modem handshake begins, the passthrough
circuit for the handset "shorts out" the modem (ie., modulator and
other data circuits) and you can carry on a normal voice conversation.
In this case you're just using the modem as a phone dialer.

Googled about the past two days to catch up on modem developments and
not much has changed regarding "garden variety" modems for home/office
use. The "voice" capabilities (beyond the raw signal processing) are
mostly found in software and all I've looked at are still file based
-- ie., record/playback a compressed audio file. Check here for some
software examples:
http://www.imptec.com/callstation.htm

FWIW, you _can_ sometimes hear some innocent person speaking at the
other end of a data dial-out -- usually cursing about the strange
noise

> Aren't voice modems capable of this?
>
> cheers,


I think you might be able to build an app that would accept a voice
input stream from another app and send it out a "voice connection" on
the modem. That is I _think_ the "on chip" hook for voice apps is
generic enough to allow this, but for the life of me I wouldn't want
to wrestle with the timing, dialing, codec, and data transfer issues
involved -- I would just pick up a phone

Doing this with an app which handles incoming VoIP (which is h.323
based -- like netmeeting) and translating(?)/transfering that voice
stream to a modem app that decodes/relays the analog voice content
onto a POTS line (which is already dialed out and connected) seems
like a lot of work. Maybe that's why there are commercial companies
that offer this sort of VoIP-POTS interconnection. High quality
digital PBX networks can too. Eventually, the phone lines will likely
be 100% digital, but we're not there yet -- maybe not for many years
as no one sees enough $ in such an expensive upgrade.

hth,
prg
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Floyd L. Davidson
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      09-13-2004
(E-Mail Removed) (P Gentry) wrote:
>"C3" <_> wrote in message news:<4140e475$0$30576$(E-Mail Removed). au>...
>> The only news to me is that voice modems are not capable of performing the
>> very limited task needed of them.

>
>Depends on what you mean by "limited". The "voice" in voice modems
>refers to the dsp and codec firmware that _digitizes_ the analog voice
>stream (and vice versa).


That doesn't seem to be the case. There are variations, and
some modems are indeed limited as you say (which hardly seems to
be a limit!), but others are not. (I hadn't realized the extent
of what these modems are capable of doing. But a quick look at
the web site you provided below, plus a little searching with
google provided all kinds of interesting information.)

Typical consumer modems might be classified as:

1) Data
2) Data and FAX
3) Data, FAX and voice
A) full duplex able
B) half duplex only
4) Data, FAX, voice and speakerphone

I was assuming the speakerphone capability was what a "voice
modem" had, but it seems that is not the case. However, the
capability of a voice modem without the speakerphone part is
*much* more useful than one with just the speakerphone
capability and not the DSP functionality available with the less
able "voice modem".

>It's the software that actually provides
>what we, as users, think of as the functionality. Ie., voice mail,
>answering machine, video phone (haven't seen one of those in a while),
>etc. Voice mail and fax are probobaly the two most used "extras"
>beyond simple data linking for dial-up networking.


True.

>> I always believed that voice modems are simply modems that can receive a
>> signal through a 3.5" minijack and pass it onto the phone line, and also to
>> send out the sound from the phoneline onto another 3.5" minijack plug. These
>> two can be connected to the input and output of a soundcard.

>
>"Everyone" (me too) has tried this at one time or other -- these lines
>(sound card to modem) won't "match" for one thing and the other
>problem is that the input/mic jack on the modem is just to _record_ a
>message. Obviates the need for a separate sound card for input _or_ a
>"speakerphone" (mic and speackers). A person-in-the-flesh doesn't
>really need a modem to "speak" on the wire -- that's what POTS and
>handsets are for.


But if you use the right modem (a voice modem with speakerphone
capability) there *is* that capability. And if you don't use a
speakerphone modem, the you merely need to use a sound card to
interface to a handset and pass the digitized audio to and from
the modem via the serial port. And obviously that is much nicer
with a modem capable of full duplex operation than it would be
with one only capable of half duplex, so the right modem makes
a big difference in how useful this is.

(As to the idea that the modem lines don't match on the sound
card, that isn't true. Most sound cards have two input lines
and one output. The two inputs are a high impedance and low
impedance. The modem might well have the same thing. Or either
of them may be limited to a low impedance output and a single
high impedance input. Matching to a low impedance input if you
have only a high impedance output device is difficult, but
matching a high impedance input when you have a low impedance
output is just a matter of one or two resistors. That's why if
they go cheap, the only input will be high impedance.)

>> The only thing left is to dial the number, that's just an ATDT away, isn't
>> it?

>
>All modems _can_ dial out. The problem is that without human
>intervention (lifting up the handset, eg.) or some software app the
>modem will try to contact another _data_ modem. If you lift the


Not true. The modem might well be configured to *respond* if
another data modem answers, but in fact it doesn't necessarily
care if that happens or not. Of course the most common use is
to set a timer telling the modem to hang up if no data
connection is made, but that is merely a matter of modem
configuration. It does not require either human or application
software intervention with each call.

>handset before the modem/modem handshake begins, the passthrough
>circuit for the handset "shorts out" the modem (ie., modulator and
>other data circuits) and you can carry on a normal voice conversation.


There is no "passthrough circuit" that shorts out the modem on
most modems. Some do have manual switches on the front panel to
connect a telset to the line instead of the modem, but that
isn't what is being used.

Most modems have a "passthrough circuit" which may or may not
(it depends on the modem) disconnect the telset line as soon as
the modem goes off hook. That is why there are two RJ-11 jacks
on the back of the modem. Some modems don't cut the telset line
when the modem is active though. With those modems it is very
easy to use that jack for a telset and have the computer use the
modem as a dialer.

> In this case you're just using the modem as a phone dialer.
>
>Googled about the past two days to catch up on modem developments and
>not much has changed regarding "garden variety" modems for home/office
>use. The "voice" capabilities (beyond the raw signal processing) are
>mostly found in software and all I've looked at are still file based
>-- ie., record/playback a compressed audio file. Check here for some
>software examples:
>http://www.imptec.com/callstation.htm


A useful URL. It does *not* support what you are saying though! It
*clearly* indicates that the modem's hardware facilities are a major
part of the voice capabilities, and that when coupled with a computer
can do *exactly* what the OP wants to do. Moreover, it can be done
*much* easier than I was thinking! I didn't realize the modem would
do the digital/analog conversion, and I thought the sound card was
necessary for that. Obviously that is not the case, which makes it
all *much* nicer!

Instead of requiring software that utilizes the sound card's DSP,
all the OP needs is software that converts incoming IP data to whatever
format the modem will accept, and feed it directly to the modem over
the RS-232 link. No external audio connections are required at all.

Given the descriptions provided on the URL you provide above, that
appears to work exceedingly well (given the right modem at least).

>FWIW, you _can_ sometimes hear some innocent person speaking at the
>other end of a data dial-out -- usually cursing about the strange
>noise


BULLSHIT. Why do you keep saying things like that? Have you
*ever* answered a ringing phone and had a calling data modem
give you a blast of data tones? No! And the reason is because
the *originate* modem is absolutely silent until the *answering*
modem sends tones.

In FAX mode a modem is slightly different, and sends a very
short bleep of start tone at regular intervals to activate the
silent answering modem.

In *neither* case is there any "strange noise" that somebody is
left cussing at. (Unless someone is *purposely* dialing out and
forcing the modem into answer mode just to annoy people. That
has no useful purpose, as no data modem will respond to it.)

>> Aren't voice modems capable of this?


Yes indeed they are!

>> cheers,

>
>I think you might be able to build an app that would accept a voice
>input stream from another app and send it out a "voice connection" on
>the modem. That is I _think_ the "on chip" hook for voice apps is
>generic enough to allow this, but for the life of me I wouldn't want
>to wrestle with the timing, dialing, codec, and data transfer issues
>involved -- I would just pick up a phone


Look at the web page you cited! That is *exactly* the kind of
applications they are discussing!

>Doing this with an app which handles incoming VoIP (which is h.323
>based -- like netmeeting) and translating(?)/transfering that voice
>stream to a modem app that decodes/relays the analog voice content
>onto a POTS line (which is already dialed out and connected) seems
>like a lot of work.


No more work than any of the answering machine, voice mail, or
whatever applications. Geeze, I don't know about you but I'm
all too often answering the phone to be presented some short
computer generated message asking me to hold the line until some
real asshole answers. They've got about 1.37 seconds to perk my
interest before I hang up on 'em...

This is just *not* something that is difficult or magic in any
way. The programming necessary to do it has been being done in
telephone switching systems for 30 years now! The fact that
consumer products have now become available at prices making the
same programs useful in products a customer might like to use is
the only thing that is "new", and frankly that isn't new either
given the 10 years that it's been available. The only thing
perhaps "new" is an almost totally ubiquitous Internet that we
have today, whereas ten years ago few people had even heard of
it.

>Maybe that's why there are commercial companies
>that offer this sort of VoIP-POTS interconnection. High quality
>digital PBX networks can too. Eventually, the phone lines will likely
>be 100% digital, but we're not there yet -- maybe not for many years
>as no one sees enough $ in such an expensive upgrade.


That is indeed a pretty good summary!

For those of us who've been taughting digital services for
decades now (ISDN: It Still Does Nothing), the advent of VoIP is
something of a long sought for magic key that will open the
pandora's box.

Consider a little history with a different perspective:

In the mid-1980's the Internet existed, and almost nobody in the
telephone industry new what it was. Those who did saw a need
for digital data services, but could not convince anyone to
offer them. Hence the R&D people, who understood computer
networks, developed ISDN, and the operations folks, who didn't
understand computers or networks, said "What for?" The R&D
folks said "It's a needed service.", and the Ops folks said "Who
will pay for the investment required?". So ISDN was not
installed, because the Ops folks did not see a market!

Instead, modem companies spent millions on R&D to develop first
v.34 and then v.90 modems, and made *billions* of bucks. That
is what the telephone industry missed out on because of the
Pointy Haired Bosses that inspired Scott Adams to create the
Dilbert cartoons. Adams, of course, worked in the telecom
industry as an ISDN applications development engineer!

By 1995 things started to change, and common people began to
hear about The Internet. But even then telecom industry
management just simply could not grasp what it meant. That led
to massive upheavals! (You might remember that AT&T went
through about 3 or 4 CEO's in a two year period trying to find
one that could force the in-place upper and middle management of
AT&T out of the old concepts of what a telephone company is.)

It has been an uphill battle getting telecom management to make
changes in the traditional concepts of what the industry is.
And VoIP is the death warrant for traditional analog, circuit
switched, message traffic!

Just as 10 years ago virtually every company that did not figure
out how to adjust their business methods to make use of the
Internet found themselves out of business or bought out by new
management, the same thing is about to happen with digital voice
services.

--
FloydL. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) (E-Mail Removed)
 
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      09-16-2004
(E-Mail Removed) (Floyd L. Davidson) wrote in message news:<(E-Mail Removed)>...
[snip]

> It has been an uphill battle getting telecom management to make
> changes in the traditional concepts of what the industry is.
> And VoIP is the death warrant for traditional analog, circuit
> switched, message traffic!
>
> Just as 10 years ago virtually every company that did not figure
> out how to adjust their business methods to make use of the
> Internet found themselves out of business or bought out by new
> management, the same thing is about to happen with digital voice
> services.


Thought you might be interested in this:
http://www.voip-info.org/tiki-index.php

regards,
prg
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