madden@sdcc3.UUCP (Jim Madden) (12/10/84)
My campus is about to embark on project that will replace lots of four wire data circuits supplied by the telephone company with connection boxes on a broadband cable. A part of the project involves installation of the local wire that will connect terminals and computers to network boxes one or two offices away. To minimize labor costs for this part of the project, we plan to use RJ11 6 wire modular plugs, wall sockets and RS232 connectors of the kind supplied by Nevada Western or Modtap. The questions for the network are: Have other institutions done similar things and can they provide us with insights into the pitfalls facing us? Is there any standard for the association (by color code or location on the RJ11 jack) of the individual leads in the cables and the pins of the RS232 connector? In the absence of standards, are there well know pieces of equipment from IBM, ATT, or other companies that we should regard as an effective standard? Although four wire circuits have been sufficient for most of our terminal connections in the past, in this project we plan to install six wire circuits for future flexibility. We've chosen 6 wires primarily since this seems to provide adequate signaling in both directions and because such circuits can use RJ11 connectors. More wires require significantly more expensive equipment. Are we making a mistake here? Does anyone have any late breaking information on broadband attachment equipment for terminal-to-host, host-to-host and micro-to-anything that will help us make a choice of such equipment in the next month? In a week or two, I'll summarize any useful information I receive. Jim Madden sdcsvax!madden
phil@amdcad.UUCP (Phil Ngai) (12/12/84)
> My campus is about to embark on project that will replace lots of four > wire data circuits supplied by the telephone company with connection > boxes on a broadband cable. A part of the project involves > installation of the local wire that will connect terminals and > computers to network boxes one or two offices away. To minimize labor > costs for this part of the project, we plan to use RJ11 6 wire modular > plugs, wall sockets and RS232 connectors of the kind supplied by Nevada > Western or Modtap. Is 6 wire enough? Let's see: TxD, RxD, GND, CTS, RTS, DTR, DCD. If you don't have modems it might be. Otherwise, perhaps not. We are using 8 wire. It ties in nicely with the use of 25 pair cable and 258A "harmonicas". -- I'm not a programmer, I'm a hardware type. Phil Ngai (408) 749-5790 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!phil ARPA: amdcad!phil@decwrl.ARPA
coffler@grok.DEC (Jeff Coffler) (12/13/84)
>My campus is about to embark on project that will replace lots of four >wire data circuits supplied by the telephone company with connection >boxes on a broadband cable. ... >Is there any standard for the association (by color code or location on >the RJ11 jack) of the individual leads in the cables and the pins of the >RS232 connector? I don't know about any standards here, but with the typical "harmonica", you really don't need to worry about it. Plug the harmonica into both ends, plug the RJ11's into the harmonica, and presto. You very well may prefer to use a distribution panel on one end (i.e. the computer end); if you get the equipment from the same supplier, you should have no troubles. >In the absence of standards, are there well know pieces of equipment >from IBM, ATT, or other companies that we should regard as an effective >standard? AT&T themselves sell the harmonicas for 4, 6, and 8 wire implementations. AT&T uses them in all sorts of ways (especially with on-site telephone equipment, like the Horizon). As standards go, AT&T has the most out, so they are probably closest to setting a standard ... (there may indeed be a standard, but I don't know of any) >Although four wire circuits have been sufficient for most of our >terminal connections in the past, in this project we plan to install >six wire circuits for future flexibility. We've chosen 6 wires >primarily since this seems to provide adequate signaling in both >directions and because such circuits can use RJ11 connectors. More >wires require significantly more expensive equipment. Are we making a >mistake here? Yeah, I do believe that's a mistake. Regardless of 4-wire, 6-wire, or 8-wire, the costs are the same for the connectors. The only problem is that, for an 8-wire installation, you need twice the number of cable runs as you would for a 4-wire installation (you use twice the number of wires). If your equipment is using XON/XOFF protocol, then 4 wires is really all that you need ... modems and/or CTS handshaking require more pins. Your computer equipment (plus future plans for computer equipment) should probably dictate just how many wires you use. If you use XON/XOFF type of handshaking, and intend to continue (a surprising number of terminals can ONLY do XON/XOFF handshaking), then 4 wire is fine for local terminals (i.e. terminals that are directly connected, not modem terminals). We used the same wiring for modems and for terminals, so in our case, we just ran 8-wire all the way. -- Jeff
smh@mit-eddie.UUCP (Steven M. Haflich) (12/15/84)
There seems agreement that four conductors suffice for most terminals, but that RS232 to modems and other more exotic exotic may require. In the particular case of modems, why not just run the phone line directly to the user's location??? This will take fewer conductors than even the most degenerate RS232: two!! Actually, certain types of phone service connections, e.g. RJ41S/45S, use four, six, or more conductors. The extras do things like indicate whether the line should be conditioned for voice or data transmission, Such services are likely to become more common as time passes. Also, many currently-available and plausible non-modem devices still require more than four-wire RS232 -- certain printers for example.
mark@cbosgd.UUCP (Mark Horton) (12/16/84)
I'm beginning to see quite a bit of use of the 8 connector RJ31X jack for RS232 connections. (It's basically a fat RJ11C modular phone jack.) There are three configurations that I know of: (1) That used by AT&T Datakit (2) That used by the AT&T 3B2 (3) That used in an Able DEC distribution panel. Since the 3B2 is likely to see significant use, and since Able has indicated a willingness to use the AT&T configuration, it seems like the best candidate for a de-facto standard. Sorry, I don't know what the configuration is, or I'd post it. Would someone who has a 3B2 handy please check their manual and post the appropriate pin configuration?
ron@brl-tgr.ARPA (Ron Natalie <ron>) (12/17/84)
> My campus is about to embark on project that will replace lots of four > wire data circuits supplied by the telephone company with connection > boxes on a broadband cable. A part of the project involves > installation of the local wire that will connect terminals and > computers to network boxes one or two offices away. To minimize labor > costs for this part of the project, we plan to use RJ11 6 wire modular > plugs, wall sockets and RS232 connectors of the kind supplied by Nevada > Western or Modtap. RJ11's are just fine if you don't plan to plug and unplug them much. They aren't designed to handle that and do break easily. It offends my sense of order to use them on terminal lines almost as much as it would to use 110v plugs, I'm afraid that if two things can be plugged into each other, they will, and some terminal will blow up when it get's the ring voltage. -Ron
bob@islenet.UUCP (Robert P. Cunningham) (12/19/84)
I use the same scheme as Darlabs Inc. does with their Mod-Tap (tm)
components. I suspect AT&T components use similar wiring. There are
actually several schemes:
4-wire, based upon the RJ11-series plugs & jacks
6-wire, also based on the RJ11
8-wire, based upon the RJ45/RJ13 series
I'm only detailing the 4 & 6-wire arrangements here, but surprisingly,
it all works together. RJ11 plugs actually fit into the RJ45 jacks,
and even work if the wiring combinations are correct.
If you take an RJ11 plug (regular modular phone plug at the end of a cord),
and look at it from the top -- with the key (plastic nib with the little
lever) on the BOTTOM, the modular wire numbers are as follows:
1 2 3 4 5 6
If you have an ordinary single-line RJ11, look at it very carefully.
You'll see that there are actually six little grooves for contacts -- but
only the middle four actually have metal in them, which I'll call:
2 3 4 5
The Mod-Tap coresponding RS232 pin assignments are as follows:
system terminal modem
modular DTE DTE DCE
1 20 20,4
2 2 3 2
3 6,8 6,8,20 8
4 3 2 3
5 7 7 7
6 22 22
(jumper 4&5) (jumper 4&5) (don't jumper 4&5)
Thus, you can use a 6-wire RJ11 to connect a computer system distribution
panel to a modem. Using the exact same modular jack, you can also plug in
a terminal, with a 4-wire RJ11 (there are different TelCo suffixes on the 4
vs. 6 wire RJ11's).
To do this right, you need several things: 1) RS232-plug-to-modular-jack
adapters (actually different ones for the three different columns above,
in whatever RS232 gender applies for your equipment); 2) "harmonicas" which
have either 12 modular jacks (for 4-wire connections) or 8 modular jacks
(for 6-wire connections) -- and a 50-pin Telephone connector (aka
"Champ" connector).
You'll also need 4 and/or 6-wire modular cable (typically comes in 500'
rolls), a bag of 4 and/or 6-wire plastic modular plugs to put on the ends,
and a special tool that crimps the plugs onto the wire to make modular
cords of any length (el cheapo tools with plastic dies available at
Radio Shack for under $20; tools with steel dies run about $150 -- you
get what you pay for).
Then, you can use regular vinyl-covered 25-pair telephone cable for trunk
lines between the harmonicas (presumably one end at the computer, the other
end at a room or close cluster of rooms with terminals). Note that the
standard phone company 25-pair wire is fairly small gauge (#24, I think),
and suitable for RS232-type signals only over a fairly limited distance
(I use larger-gauge wire for runs 500 feet or more).
[Note that these wiring schemes are not completely compatible with
"group termination" 25-wire cabling on Micom and other PACX's.
Special inter-connect cables (which you can make yourself) are required
to use both together.]
You can also get "harnesses" that have the 50-pin connector at one end, and
a set of pigtails with RJ11 modular jacks on the other.
Modular patch panels are also available, and very handy. They've 50-pin
connectors on the back, modular jacks on the front, and you can cross-patch
using modular cords.
Then there's the old standby: the "R66" punch-on terminal block that takes
25-pair or 50-pair cables and allows you to punch on individual 4/6 (or
whatever) wire sets for running individual terminal lines.
For a reasonably-good explanation about how all this works, take a look at
Dave Mallery's article "The maze untangled; a solution to the terminal
distribution problem" in the May 1984 issue of The DEC Professional.
Most of the equipment you can probably buy from the supply company
subsidiary of your local phone company. A whole collection of these (and
other related equipment) is manufactured by Darlabs Inc. (phone
617-456-3500 and ask for their catalog, it's worth looking at even if you
don't buy their brand). Darlabs prefers to sell through their distributors,
notably Glascal (201-768-8082, and their catalog is also worth having for
the extensive listings of these and other data communications equipment).
At the moment, I'm in the process of wiring up Yet Another Building for
terminals here at the University of Hawaii. Traditionally, we've been
using multiple runs of 4 or 6-wire TelCo-type "station wire" in conjunction
with R66 blocks -- and solder on the necessary RS232 plugs. This time, I'm
using the 25-pair cabling system with modular harmonicas, modular patch
panels and RS232-to-modular adapters. Sure goes in a lot quicker.
Incidentally, we're still using some inter-building leased phone lines for
terminals. What we order is a "4-wire control circuit" rather than two
single-pair leased phone lines.
--
Bob Cunningham ..{dual,ihnp4,vortex}!islenet!bob
Honolulu, Hawaii