1 Aug
2005
1 Aug
'05
8:02 p.m.
Essentially the layout would be this. I have a computer with 4 internal
modems in it. Has to be internal, I can't do this with external
modems/serial ports. Somehow I get it configured so that I can telnet from
the internet to this "emulator" and it directs my telnet session to one of
the 4 free analog lines.
Now, there's some solutions like lantronix UDS devices, where the device has
an ethernet jack and a 25 pin serial port and it can be set to emulate an
external modem, so folks can telnet to this device and it then tricks the
computer into thinking a modem connection is made...
...but my scenario is different in that I want the connection going to the
PC to still be analog lines. So, this device would have to have some sort of
modem emulation of its own.
It sounds sort of off-the-wall, but I wanted to run it by the group to see
if it rang any bells. Maybe there's some situation where such a device
would have been developed, but I'm not seeing the connection yet. Perhaps
if you were putting a multiline BBS system (that didn't support external
modems) on a local LAN? Maybe that's stretching the boundaries of sensible
communications a bit :)
Pete
2 Aug
2 Aug
2:34 a.m.
On Mon, 1 Aug 2005 23:02:33 -0400
"Pete Bartusek" <pete at bartusek.com> wrote:
Essentially the layout would be this. I have a
computer with 4
internal modems in it. Has to be internal, I can't do this with
external modems/serial ports. Somehow I get it configured so that I
can telnet from the internet to this "emulator" and it directs my
telnet session to one of the 4 free analog lines.
Get a terminal server with
"reverse telnet" capability, connect modems
to the serial lines, connect the modems back-to-back to the POTS lines
of the internal modem and that's it. OK, most likely you have to do some
tricks to get a ring signal when someone connects via telnet to the
terminal server. E.g. it may be enough to use DTR from the treminal
server to initiate a ring tone generator on the POTS line between the
modems. Or get a old == cheap small analog PBX...
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
7:45 a.m.
On Tue, 2 Aug 2005, Jochen Kunz wrote:
Get a terminal server with "reverse telnet"
capability, connect modems
to the serial lines, connect the modems back-to-back to the POTS lines
of the internal modem and that's it. OK, most likely you have to do some
tricks to get a ring signal when someone connects via telnet to the
terminal server. E.g. it may be enough to use DTR from the treminal
server to initiate a ring tone generator on the POTS line between the
modems. Or get a old == cheap small analog PBX...
It won't work to just plug the modems together by their phone jacks. You
still need line voltage or else they won't work.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
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11:19 a.m.
On Tue, 2 Aug 2005 07:45:26 -0700 (PDT)
Vintage Computer Festival <vcf at siconic.com> wrote:
It won't work to just plug the modems together by
their phone jacks.
You still need line voltage or else they won't work.
Yes. But
"better" modems have a "leased line" mode where they don't need
extra voltage. If this fails there is still the way with the 9 V
battery, as already mentioned. With this you only need "ATA" (IIRC)
to initiate a carrier handshake between the modems. Or configure the
modem on the terminal server side to do "auto dial at DTR"...
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
11:26 a.m.
On Tue, 2 Aug 2005, Jochen Kunz wrote:
On Tue, 2 Aug 2005 07:45:26 -0700 (PDT)
Vintage Computer Festival <vcf at siconic.com> wrote:
Still doesn't solve the multiplexing problem (which a PBX does solve).
Unless you don't need multiplexing, in which case you should eat your foot
for dinner.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
It won't work to just plug the modems
together by their phone jacks.
You still need line voltage or else they won't work.
Yes. But
"better" modems have a "leased line" mode where they don't need
extra voltage. If this fails there is still the way with the 9 V
battery, as already mentioned. With this you only need "ATA" (IIRC)
to initiate a carrier handshake between the modems. Or configure the
modem on the terminal server side to do "auto dial at DTR"...
12:33 p.m.
On Tue, 2 Aug 2005 11:26:05 -0700 (PDT)
Vintage Computer Festival <vcf at siconic.com> wrote:
Still doesn't solve the multiplexing problem
(which a PBX does solve).
Unless you don't need multiplexing,
Why would you need automatic multiplexing?
With the described setup you get a maping:
TCP/IP port <=> modem <=> BBS port
I.e. each BBS port gets a different TCP/IP port. If user A is connected
to TCP/IP port 1 no other connections are accepted on that TCP/IP port.
If user B wants to connect he doesn't get a connection when telneting to
TCP/IP port 1. So he has to retry with TCP/IP port 2 etc. Not that nice
(manual multiplexing by the end user), but it is the simplest solution.
Alternative:
If you use a TCP/IP capable computer with multiserial card insted of the
terminal server you can write a custom application. It handles the
TCP/IP to serial port mapping and moving the bits back and forth of the
TCP/IP connection and serial port. It is easy to design this application
in a way that it accepts multiple TCP/IP connections to the _same_
TCP/IP port. The application keeps book on what serial lines / modems /
BBS ports are already in use so that it can connect a new TCP/IP
connection to the first free serial line == BBS port. This way you get
automatic multiplexing for the expense writing the multiplexing
application yourself.
in which case you should eat your foot for dinner.
Pardon?
--
tsch??,
Jochen
Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
11:52 a.m.
It won't work to just plug the modems together by
their phone jacks. You
still need line voltage or else they won't work.
That depends on the modems.....
I've not seen schematics for any recent modems, but all the old ones (up
to 2400 bits/second) used a transformer to couple the audio, that
transformer being capacitively coupled to the line. There was no DC path
through that part of the circuit, therefore, so the audio transmission
shouldn't depend on line voltage.
If the unit uses relays for off-hook switching, etc, then there shouldn't
be any problem with that part of the cirucit needing line voltage either
(semiconductor switches might need the line voltage for bias).
Obviously the ring detector detects ringing voltage from the line.
-tony
8 a.m.
Jochen Kunz wrote:
On Mon, 1 Aug 2005 23:02:33 -0400
"Pete Bartusek" <pete at bartusek.com> wrote:
I'm certain that I've done this by connecting 2 modems back-to-back,
although it's been a very long time.
There's an AT command to open the line without a ring signal.
A Livingston Portmaster 2 or 2E is nice makes very nice terminal or
console servers, have dial-in/dial-out capability, are well-documented,
and very cheap. They're also a lot more common than the various DECservers.
As a matter of fact, I have a 10-port 2E and a 20-port 2E for sale.
Make a silly offer.
Doc
Essentially the layout would be this. I have a
computer with 4
internal modems in it. Has to be internal, I can't do this with
external modems/serial ports. Somehow I get it configured so that I
can telnet from the internet to this "emulator" and it directs my
telnet session to one of the 4 free analog lines.
Get a terminal server with "reverse telnet" capability, connect modems
to the serial lines, connect the modems back-to-back to the POTS lines
of the internal modem and that's it. OK, most likely you have to do some
tricks to get a ring signal when someone connects via telnet to the
terminal server. E.g. it may be enough to use DTR from the treminal
server to initiate a ring tone generator on the POTS line between the
modems. Or get a old == cheap small analog PBX...
7:33 a.m.
On Mon, 1 Aug 2005, Pete Bartusek wrote:
...but my scenario is different in that I want the
connection going to the
PC to still be analog lines. So, this device would have to have some sort of
modem emulation of its own.
I doubt you'll find anything to do this, not that they don't exist, but if
you do it'll probably be outside your price range.
Sounds like a custom solution to me. Get a Linux box with a modem and an
external switch (in this case "switch" meaning a PBX of some sort). A
Panasonic 606 is perfect for what you need: small, easy to program (the
default programming will work), and it's a hybrid so it uses both
proprietary digital sets and normal analog sets (auto-sensing). They're
also abundant and probably cheap by now. In fact, I think I have one I
can sell you. A Panasonic 1232 is the same thing with just more ports (12
CO trunks, 32 stations) but overkill. Plug the 4 modems of the target box
into one of the 16 extensions, then plug the modem on the Linux gateway
into a fifth extension. The Linux modem can then dial directly into any
one of the 4 target machine modems by dialing its extension number.
Then, write some software to do the conversion :)
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
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[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
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7:52 a.m.
On Tue, 2 Aug 2005, Vintage Computer Festival wrote:
Panasonic 606 is perfect for what you need: small,
easy to program (the
Sorry, I meant the Panasonic 616. I just remembered there's also the 308
which is even better for your purposes as it would be smaller with only 8
stations instead of 16.
The other nice thing about the Panasonic switches is that they are ready
to go. They have modular phone jacks so you just power it up, plug in
phones, and dial away. Extensions are programmed by default as 101, 102,
103, etc.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
2:57 p.m.
Vintage Computer Festival wrote:
A Panasonic 606 is perfect for what you need: small, easy to program (the
default programming will work), and it's a hybrid so it uses both
proprietary digital sets and normal analog sets (auto-sensing). They're
also abundant and probably cheap by now.
I have one - I use it for testing modems (or I did, back in the day).
I paid $500 a long long time ago - probably much cheaper now.
And they were a great pbx at the time. Now days I buy $9.95 PCI FXO
cards on ebay and use asterix :-) who woulda thunk that voip would
really work?
-brad
6864
days inactive
6864
days old
10 comments
6 participants
participants (6)
-
ard＠p850ug1.demon.co.uk -
brad＠heeltoe.com -
doc＠mdrconsult.com -
jkunz＠unixag-kl.fh-kl.de -
pete＠bartusek.com -
vcf＠siconic.com