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Connectors for Okidata Serial Printers to Unixware

Connectors for Okidata Serial Printers to Unixware

Connectors for Okidata Serial Printers to Unixware


I need to connect 2 Okidata Printers (Microline 390/391 & Microline 591) to a SCO Unixware box via the serial ports.  Can someone tell me how to pin the RS232 connectors?  If possible (since I'm new to this area) could you give the colors to pin layouts?  I plan on using a straight through CAT 5 cable between the two RS232 connectors.

Thanks In Advance!!!


RE: Connectors for Okidata Serial Printers to Unixware

From your description I am assuming you have a DB-25 on the printer, what serial connections do you have on the UNIX box?  It also sounds like you are using modular adapters, those with a serial (DB) connector and a modular jack in the hood of the connector.  Each pin of the modular jack has a colored wire with a plug in pin for the serial plug.

That being said, I can't help you on the colors since I have seen different colors on different brands.  However, the RS-232 pinout for DB-9 and DB-25 are pretty sraight forward.  Unfortunately, implementation of the RS-232 'standard' is quite varied.

In a nutshell, you need a ground, transmit and receive.  If you implement hardware flow control or if the printer requires it, you will need to work with the control pins to make it print.  These can be tricky indeed.  Sometimes, you can fool the device by tying a few pins together at one end to make it think it is ready to print.

I normally start with my serial analyzer in the circuit and jumper the various control pins until I confirm that it is working properly, then build a cable like that.  If I had to guess, I would start like this, assuming you have a DB-9 on the computer and a DB-25 on the printer.

DB-9      DB-25

2 --------- 2
3 --------- 3
4 --------- 6
5 --------- 7
6 --------- 20
7 --------- 5
8 --------- 4

This cable assumes that:

1. the printer needs hardware flow control
2. the computer is implementing hardware flow control

Here is a link to a basic page on RS-232 pin outs.


Now...if I had to guess what to do next if that didn't work, I would shoot for this cable:

DB-9      DB-25

2 --------- 2
3 --------- 3

4           6 -|
5 -------- 7  |
6           20-|

7           5 -|
8           4 -|

In this cable we fool the printer (usually the one that is the problem) into thinking it is ready all the time by jumpering 6 and 20 together, and 4 and 5.

There are many ways of configuring this, this is one guess, hope it helps you find what you need.

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

RE: Connectors for Okidata Serial Printers to Unixware

Thanks Daron!

I guess I forgot to say what was on the Unix box.  This is a brand new system that I am ordering and I don't know if it will be a DB-25 to DB-25 or 9 pin yet.  But your information will help me!  These connectors will indeed have the modular jack within the connector.

Thank You for your time.


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