wtl@ulysses.att.com (Bill Langin[ftd]) (10/04/90)
Hello,
I have two modem's I want to connect directly.
Can I just take the modular telephone cord out of the wall and directly
connect the modems or do I need special cable?
I have heard I need "twisted pair" cable, but I thought that was just a
type of wire and may be a synonym for regular modular telephone cable.
Suggestions are appreciated.
Thanks,
-- Bill Langin -> My opinions are mine only... Go figure.
INTERNET: wtl@ulysses.att.com UUCP {att,decvax,ucbvax}!ulysses!wtllstowell@pyrnova.pyramid.com (Lon Stowell) (10/05/90)
IF, and it's a big IF, your two modems support a Leased Line
mode, it is fairly simple to connect them together. You will
need a standard RJ-11 extension cord and a pair of cutters,
soldering iron etc.
The problem is that the Xmit and Rcv leads are swapped in the
telco network......
Chop the extension cord in half, and then solder these pairs
together...
Take the Red and Green Wires from one half and solder
them to the Yellow and Black wires from the other half.
Red and Green form the "normal" Xmit pair, Yellow and Black
the Receive pair....
Plug it in, and have fun.
If the modems are dial-up, there is no real way to just hook
them together....
BTW, why not just create a null-modem cable for the two DTE's
and hook them together directly?cedman@lynx.ps.uci.edu (Carl Edman) (10/05/90)
In article <1990Oct5.004640.25706@robobar.co.uk> ronald@robobar.co.uk (Ronald S H Khoo) writes: wtl@ulysses.att.com (Bill Langin[ftd]) writes: > I have two modem's I want to connect directly. > Can I just take the modular telephone cord out of the wall and directly > connect the modems or do I need special cable? Is what you mean like this ? computer <---> modem <----//----> modem <---> computer ^ |_ the connection you want. Well if so, here's a trick which Doreen Pechey(*) showed me: just use a telephone T connector and ignore the plug end of it. If you have such things in the USA that is :-) I refer to connectors that allow you to telephone 1 ---> T1 |----> phone socket telephone 2 ---> T2 just plug the modems into the T1 and T2 ends of the connector and ignore the plug that would go into the phone socket. No twist is required. Doreen uses this trick when giving courses teaching people how to use modems :-) My goodness, what inefficiency ! (Yes, I know this word isn't en vogue now that it is alright to have a screen blanker which uses 1 MByte+ of memory, but those of us who learned to program on computers with 512 Bytes (That is Bytes, no k, no M !) still have conditioned reflexes which force them to respond to posts like the above :-). If you want to connect 2 computers, and don't have a network then use a null-modem cable for $9.95. Null-modem means that you use 0 modems. It connects directly between the serial ports of your 2 computers (those ports, to which usualy the modem is connected) and allow you to use transfer rates orders of magnitude higher even that the advanced modems discussed in this group. Carl Edman Theorectial Physicist,N.:A physicist whose | Send mail existence is postulated, to make the numbers | to balance but who is never actually observed | cedman@golem.ps.uci.edu in the laboratory. | edmanc@uciph0.ps.uci.edu
ronald@robobar.co.uk (Ronald S H Khoo) (10/05/90)
wtl@ulysses.att.com (Bill Langin[ftd]) writes: > I have two modem's I want to connect directly. > Can I just take the modular telephone cord out of the wall and directly > connect the modems or do I need special cable? Is what you mean like this ? computer <---> modem <----//----> modem <---> computer ^ |_ the connection you want. Well if so, here's a trick which Doreen Pechey(*) showed me: just use a telephone T connector and ignore the plug end of it. If you have such things in the USA that is :-) I refer to connectors that allow you to telephone 1 ---> T1 |----> phone socket telephone 2 ---> T2 just plug the modems into the T1 and T2 ends of the connector and ignore the plug that would go into the phone socket. No twist is required. Doreen uses this trick when giving courses teaching people how to use modems :-) (*) Doreen doesn't post here, but her husband Bill does sometimes -- Hi Bill, say "thanks" to Doreen from me for this trick -- I have been using it quite a bit recently :-) -- ronald@robobar.co.uk | +44 81 991 1142 (O) | +44 71 229 7741 (H) | YELL! "Nothing sucks like a VAX" -- confirmed after recent radiator burst! Hit 'R' <RETURN> to continue .....
wb8foz@mthvax.cs.miami.edu (David Lesher) (10/05/90)
In <129281@pyramid.pyramid.com> lstowell@pyrnova.pyramid.com (Lon Stowell) writes: >IF, and it's a big IF, your two modems support a Leased Line >mode, it is fairly simple to connect them together. You will >need a standard RJ-11 extension cord and a pair of cutters, >soldering iron etc. >The problem is that the Xmit and Rcv leads are swapped in the >telco network...... This presupposes that "leased line" == "2 pair/4 wire leased line", when in fact lots of modems have {2 wire} leased line modes that disable dropout on carrier loss, dial tone detect, and may also swamp the input to allow higher signal levels. -- A host is a host from coast to coast.....wb8foz@mthvax.cs.miami.edu & no one will talk to a host that's close............(305) 255-RTFM Unless the host (that isn't close)......................pob 570-335 is busy, hung or dead....................................33257-0335
neal@mnopltd.UUCP (10/05/90)
-> I have two modem's I want to connect directly.
-> Can I just take the modular telephone cord out of the wall and directly
->connect the modems or do I need special cable?
-> I have heard I need "twisted pair" cable, but I thought that was just a
->type of wire and may be a synonym for regular modular telephone cable.
-> Suggestions are appreciated.
If I understand you, you aren't connecting dte devices, you are connecting
telephone devices, in which something must come up with the operating voltage
and the ringing voltage. Might I suggest a small used PBX?
Or is there something that simulates this?
------------------------------------------------------------------------------
Neal Rhodes MNOP Ltd (404)- 972-5430
President Lilburn (atlanta) GA 30247 Fax: 978-4741
emory!mnopltd!neal
------------------------------------------------------------------------------ronald@robobar.co.uk (Ronald S H Khoo) (10/06/90)
cedman@lynx.ps.uci.edu (Carl Edman) writes: [ my reply to someone who wanted to know how to connect two modems together deleted ] > My goodness, what inefficiency ! Yes. I too know how to wire up a null modem cable, but that is *not* what the original poster asked for. He didn't say *why* he wanted to connect two modems together, but there *are* several perfectly normal circumstances under which people do such things -- I do this myself on many occasions. It would be much more polite if you did not immediately jump to the conclusion that everyone else is a fool. It doesn't always win you friends. Can we get back to technical discussions please ? No follouwps welcome. -- ronald@robobar.co.uk | +44 81 991 1142 (O) | +44 71 229 7741 (H) | YELL! "Nothing sucks like a VAX" -- confirmed after recent radiator burst! Hit 'R' <RETURN> to continue .....
Howard_Reed_Johnson@cup.portal.com (10/06/90)
> From: wtl@ulysses.att.com (Bill Langin[ftd]) > I have two modem's I want to connect directly. > Can I just take the modular telephone cord out of the wall and directly > connect the modems or do I need special cable? > I have heard I need "twisted pair" cable, but I thought that was just a > type of wire and may be a synonym for regular modular telephone cable. > Suggestions are appreciated. I just read through a flood of followup articles to your request, but there was a lot of misinformation there (typical for Usenet--I can often tell which answers are the best ones, often by recognizing the authors' names). My experience is this: If you just want to connect a couple of typical Hayes-compatible modems for a one-shot transfer, just take an ordinary RJ-11 phone cable and plug them into the two modems. Often, one of the machines is running software I've installed. I start by issuing the ATO command from the other machine, followed by the ATA command from my machine. At this point, communicate normally, and invoke file transfers manually from both sides. Of course, if you have a null modem cable for your *serial* ports, you can bypass the modems and get better throughput. If you do this on a regular basis (e.g., laptop file transfers), consider Lap Link or Brooklyn Bridge (about $100 for either, cables included) since they can use printer ports for even faster transfers. On the other hand, if you want to set up a network or BBS without using phone lines, none of this advice applies to your situation.
tnixon@hayes.uucp (Toby Nixon) (10/07/90)
In article <129281@pyramid.pyramid.com>, lstowell@pyrnova.pyramid.com (Lon Stowell) writes: > Chop the extension cord in half, and then solder these pairs > together... > [deleted instructions to cross over wires and solder] > If the modems are dial-up, there is no real way to just hook > them together.... Sorry, you're just wrong here! Modems do NOT care about the polarity of the Tip and Ring circuits. You can plug two dial-up modems back to back with a standard male-to-male modular cord, give one an "ATD" command and the other "ATA", and they'll connect with each other just fine! I do it all the time. > BTW, why not just create a null-modem cable for the two DTE's > and hook them together directly? In my case, it is TOO MUCH TROUBLE to uncable all of my modems from my serial ports to hook up my Mac and PC together. To connect their modems to each other, all I have to do is pull the T-connector out of the wall jack, and the two modems are left hooked together as I mentioned above. Of course, since they're both also connected to the Vax at 38,400, I usually just upload the file I want to transfer to the Vax and download it on the other machine. I also on occassion in the past wanted to transfer files locally between machines, when on one of them I didn't have a regular serial port at all, but just an internal modem (and incompatible disk drives; such as transfer files from an IBM PC to an Apple IIc). -- Toby ----------------------------------------------------------------------------- Toby Nixon, Principal Engineer Fax: +1-404-441-1213 AT&T: !tnixon Hayes Microcomputer Products Inc. Voice: +1-404-449-8791 CIS: 70271,404 Norcross, Georgia, USA BBS: +1-404-446-6336 MCI: TNIXON UUCP: ...!uunet!hayes!tnixon Internet: hayes!tnixon@uunet.uu.net
neal@mnopltd.UUCP (10/17/90)
->In article <129281@pyramid.pyramid.com>,
->lstowell@pyrnova.pyramid.com (Lon Stowell) writes:
->
->> Chop the extension cord in half, and then solder these pairs
->> together...
->> [deleted instructions to cross over wires and solder]
->> If the modems are dial-up, there is no real way to just hook
->> them together....
->
->Sorry, you're just wrong here! Modems do NOT care about the
->polarity of the Tip and Ring circuits. You can plug two dial-up
->modems back to back with a standard male-to-male modular cord, give
->one an "ATD" command and the other "ATA", and they'll connect with
->each other just fine! I do it all the time.
->
->> BTW, why not just create a null-modem cable for the two DTE's
->> and hook them together directly?
->
->In my case, it is TOO MUCH TROUBLE to uncable all of my modems from
->my serial ports to hook up my Mac and PC together. To connect their
->modems to each other, all I have to do is pull the T-connector out
->of the wall jack, and the two modems are left hooked together as I
->mentioned above.
As one of the earlier posters of the one of the dumber answers to this
question (involving buying an old pbx) ...
I assumed that the original poser knew enough to do a null modem. What
about the situation where you need to test the ring, answer, and line loss
situation? Like uhhh, testing a communications concentrator, Email box
system, etc, and you don't or can't get 24 phone lines to do it? Are
there cheaper ways around that block?
------------------------------------------------------------------------------
Neal Rhodes MNOP Ltd (404)- 972-5430
President Lilburn (atlanta) GA 30247 Fax: 978-4741
emory!mnopltd!neal
------------------------------------------------------------------------------