It is possible to make up any RS-232 cable required using a single type of cable with an adaptor at each end - the trick lies in the adaptors. In total, eight different types of adaptor are required to cover all possibilities of:
As already stated, you need to have a total of eight types of adaptor available. The following tables gives all the detail you need to make up all eight types. Full details can be found the in the R&D drawings quoted.
The first step is to buy the unwired adaptors. These come as a pre-wired RJ-45 jack with push-fit D-type pins on the ends of the wires. The kit also includes the D-type and a nice moulded bit of plastic to hold it all together.
|9 pin||25 pin|
|RS stock code||447-667||447-673||447-689||447-695|
Each adaptor has to be assembled before use. This tables shows you which wire to stick in which hole - it doesn't matter whether you're assembling a plug or a socket here, they both use the same pin numbers.
|9 pin||25 pin|
|R&D drawing no.
|RJ-45 pin no.||Wire colour||Wire colour
(New RS adapters)
|D-type pin no.|
Ok, so now you have a whole bunch of adaptors, but how do you use them? The trick is to identify the piece of equipment to be connected, and then remember that every cable you ever need has a Type-A adaptor at one end and a Type-B adaptor at the other end with a piece of straight UTP (or FTP/STP) cable in between. Note that if a reversed (not crossed) cable is used then one adaptor should be swapped for the opposite type (i.e. the cable becomes A-to-A or B-to-B).
The only slight catch left now is that you need to know what is a Type-A and what is a Type-B, which is where the next table comes in. It is suggested that each adaptor in use is labelled as shown in the table with the suffix -A or -B as appropriate, thus Sun-A, VT220-B and so on.
|CO9/21||Low Sampling Frequency Adaptor||LSFA-A||9P-1|
|CO10/21||Serial-Parallel Interface Box||SPIB-A||9P-2|
|Bay Switch 350||Bay350-A||9S-2|
|Psion Series 3c and 5||Psion-A||9P-2|
Some pieces of equipment have in-built RS-232 connections on RJ-45 jacks. To connect to these, you can still use the standard piece of straight cable with an adaptor on the end, and you still follow the same rules of Type-A at one end and Type-B at the other. The following table shows how the in-built RJ-45 is wired - you need the opposite type adaptor at the other end.
|Equipment||RJ-45 wired as|
That's all there is to it! You can now make up any cable you need between any two pieces of equipment listed above without having to worry about whether it's a plug or a socket, or whether it should be a null-modem cable or a straight cable. Enjoy!
The following examples may make things a little clearer.
Any of the following four cables will connect a Sun console port to a VT220 terminal.
Any of the following four cables will connect a Sun console port to a CS200.
Either of the following two cables will connect a Sun console port to a Lantronix RAS.
Option one is usually used (so that a terminal can be easily plugged in without changing the adaptor) however option two allows the use of a standard length of UTP/FTP/STP cable. If needed, two straight cables can be joined using a coupler (available as RS part 186-3054, not CEMASTed) to make a single reversed cable.
Any of the following three cables will connect a pair of laptop PC's together.
Either of the following two cables will connect a Psion Organiser (Series 3c, Series 5 or Siena) to a Lantronix LRS-series Remote Access Server (aka terminal server)
...to the following people for their invaluable help in producing these adaptors:
|Written by Mike Ellis. All errors are completely my own work.|
|Version 0.3 © BBC R&D 1997-8|