The RS standard specifies a maximum cable length of 75 feet at bits per second. In practice, lenghts of to feet work just fine. You simply push these pins into the holes in the RS connector and then snap the adapter housing on. The color coding of wires in RJ adapters is fairly standard. The adapters are available from many electronics stores. Hendrickson and I reproduced them without ever checking them or using them. I found confirmation of the correct pinouts here:.
Some Cisco equipment uses a similar system on RJ with different pinouts. I thought I should alert you to the fact that your conventions conflict with those employed by Motorola on some maybe all? In particular, we use MVMELX boards in many of our customer training classes look for the link to "Customer Education and Training" down near the lower righthand corner of the home page.
I'm not suggesting that you change your conventions since I'm sure a bunch of people are already using it. It might spare somebody some grief someday if you put a little caveat to this effect into your web page, however. This standard is not a cable-twist system. I put this scheme together in the summer of Thanks to folks at UC Berkeley for the idea. Their wiring is slightly different, I gather for historical reasons, but the basic idea was there. If I can find out who really originated this scheme, I'd like to credit him or her by name.
About , the scheme was picked up for the 2nd edition of the Unix System Administration Handbook , where it was given this name. Then I found out that Kenneth J. Hendrickson made a web page out of it. He graciously gave me permission to use his HTML. What you see here is a new version which is more the way I wrote it in the first place and which corrects a glaring omission: the cables must have a "twist".
When I first published this scheme in , I wrote "Maybe one day before the year 2,, the world will have a new, simple, high-speed, flow-controlled, standard type of connection for point-to-point applications currently using RS, with an adaptor available to talk to old, RS equipment. And add to this the fact that the equipment that hooks up using FireWire technology is plug-and-play and can be connected or disconnected while the system is running, and you see we indeed have come a long way.
All cable connectors are of the same type RJ You can mass-terminate the connector cables with a crimping tool. The other two hassles that remain are: Baud rate matching.
Flow control problems. All of your cables are wired the same and have the same connectors. No more changing pins on cable connectors. We will discuss this standard in detail here. The mess with RS wiring is widely known. It was the reason for starting this website. Dave Yost wanted to solve that mess once and for all, reaching as much as possible of the following goals:.
The Yost standard has however one basic advantage. Because RJ45 connectors are used, eight pins are available which makes it possible to transfer almost all RS signals. One cable for all solutions is the basis of the Yost standard. This cable is not a straight through patch cable with two RJ45 connectors crimped to each end, but a cross-cable where pin 1 is connected to pin 8, pin 2 to 7 etc.
The basic layout of this cable is shown below. In this picture flat cable is used, which is specially designed for use with RJ45 connectors. Do not use cross cables that are sold in some computer stores. Those cables cross some pairs to make the connection of two computers with Ethernet network cards possible without a hub, but these cables are not recommended for Yost systems.
The signal ground has been split in two lines to get a symmetric layout. Two common RS signals are missing on the RJ45 connector. If twisted pair cable is used with the RJ45 connectors, the following pairs are advised to minimize cross-talk between the lines: , , and When twisting this way, both data lines are twisted with their own signal ground line, adding some noise immunity.
Twisting of the handshake lines is less critical. The exact color-scheme to connect the twisted pair cable to the RJ45 connectors is not important for the functionality of the cable, but it is important for yourself to use only one color-scheme to prevent errors. Now we know how the cables are wired, it is time to define the adapter wiring for various equipment. Depending of the type of equipment, DB9 or DB25 connectors are used. The colors are defined by the Yost standard.
Please use the manual of the device or software to decide if this loop is necessary.
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