serial cabling over cat 5e 1

[eanda10]

My company still uses some dumb terminals (1930's technology) they are connected to our unix server via cat5 cable to our equinox box which basically converts it into serial lines..

we are looking to rewire and save some money so as the i.t person I was thinking about just doing the wiring my self I do have some experience in puncing down reguler cat5e jacks but can anybody tell me what would be the pinout for the serial lines (what we have now are that the wires are crimped on both ends which is really not a great way of running these wires I would love to use jacks so the wires are tied down on both ends How can this (or atlease crimp the one end and put a jack at the users end.)
from what I understand it uses a reverse pinout which I never heard of .

if I do use this reverse pinout (whatever it is ) can I use a regular striaght thru cable from jack to dumb terminal??

 

[daronwilson]

Well it IS the holiday season, I hope you are relaxed by the fire and just dreaming of serial connectivity.

I have done similar installs with IBM serials setups, we just use standard straight through Cat5e wiring and connections. Assuming you have a connector on the back of your terminal that will gives you an 8 pin modular plug or some sort, I believe you should be able to use a patch cord to a cat5 jack on the wall, and a cat5 jack on the other end with a patch cord to the equinox box. Probably best to quickly build a little test setup and see if it works. If it doesnt, you have a few options.

Personally I think you are better off installing a Cat5e structured cabling system, then make a conversion to your particular network. To do that, I'd install good quality cat5e cable, properly, teriminate it in the computer room on a standard patchrack. At the workstation end, put regular cat5e plugs and faceplates in. Now, you can test your installation with a variety of testers and make sure the wiring is ok.

I'm guessing the connector on the back of the terminal is a DB25, and that there is likely an adapter to convert that to an 8 pin modular jack. If it were me, I would make whatever conversion necessary in this adapter plug, then you can use the terminal on any cat5e wire anywhere with just straight patch cables.

It gets complicated when you mix media like that, however, it makes the most sense to me that the installed (structured cable system) media be consistant with current standards. It would make little sense to pull cat5e in, terminate it in some wierd arrangement on a plug to make old computers work. Then if (when) an upgrade takes place, you have to redo all the connections.

If the installation requires some reverse cabling, you will need to know what exactly that is. Generally I start with a working setup and use my meter to check continuity from end to end. Then I know that pin 1 at the terminal goes to pin 6 at the equinox (or whatever). Based on the wiring, I can build an adapter at the terminal end to make it work with standard Cat5 wiring.

Hope that helps, I'd need more specific details to get much closer for you.

Good Luck!


It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[wires]

Daron is steering you in the correct direction with the "installing a Cat5e structured cabling system" concept. This is the same way I handled a upgrade from termials to PC's a few years ago.

In general most serial terminal stuff uses three wires: TD(transmit data), RD(receive data) and SG(signal ground). Handshaking is handled with XON XOFF.

Just like twisted pair ethernet TD must be connected to RD on the other end of the wire. For some devices (terminals & other DTE devices) this will require a "crossover" for others "straight" wiring (modems, printers & other DCE devices) is required. Usually these "crossovers" are done at the terminal end of the run.

As far as the cabling is concerned that depends on what sort of connectors are involved. Traditionally DB25 connectors have been used for serial data but more recently RJ (phone connector) type connectors have been used.

If you have DB25 (or DB9) connectors there are adapters available to convert from DB25 to "RJ45" type jacks. Graybar Electric stocks ones from AllenTel and here are the pinouts for a "standard" three wire system:

Unix box end (II "straight&quot:
pin 2 - red wire (TD)
pin 3 - green wire (RD)
pin 7 - black wire (SG)

terminal end (X "crossed&quot:
pin 2 - green wire (RD)
pin 3 - red wire (TD)
pin 7 - black wire (SG)

A small LED type tester like this one is very helpful in troubleshooting:

http://www.trianglecables.com/mintesrsdb25.html

If your system uses hardware handshaking more wires will be involved with evem more "crossing".

Helpful hint. Mark all DB to RJ adapters with either II (two parallel lines for "straight&quot on a X (two crossed lines for a "crossover&quot. This will aid in sanity later on.

 

[InnoTech]

very true "wires"

if your terminals do not already have the DB9-25 "converter" jacks it would be a good idea to get them (future use without terminals.) I use to work for a company that our biggest client was wal-mart. as you all know wal-mart is very cheap and cost effective at all times. this was with thier network also (for the most part). when doing our "ethernet conversion" we replaced all cabling (IRC and other old crap) with cat5. for the dumb terminals we installed the DB-9 connectors that converted the pin-out at the terminal end. at the server room we installed "computone's" which were ethernet devices that would have ports for DB-9's where our cat5 could patch into. the computone would then in return patch through to the switch along with other p.c.'s ect.

in this case the cabling could be used for any device on each end. that helped when they started changing some of the terminals to p.c.'s and eventualy getting rid of the "computones" and all terminals. not in all stores though, just the new ones. (like I said, they are cheap)