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From: dave@astra.necisa.oz (Dave Horsfall)
Newsgroups: comp.dcom.modems
Subject: Re: Partial RS-232 Solution
Message-ID: <249@astra.necisa.oz>
Date: Fri, 11-Sep-87 01:12:06 EDT
Article-I.D.: astra.249
Posted: Fri Sep 11 01:12:06 1987
Date-Received: Sun, 13-Sep-87 09:08:54 EDT
References: <377@grand.UUCP>
Reply-To: dave@astra.necisa.oz (Dave Horsfall)
Organization: NEC Information Systems Australia, Sydney, AUSTRALIA
Lines: 55
Keywords: RS-232

In article <377@grand.UUCP> day@grand.UUCP (Dave Yost) writes:
>
>           Adaptor                            DCE    DTE
>           --------------------------------   -----  -----
>           Transmit Secondary Modem Control   CTS--> RTS--> ----+
>           Transmit Primary Modem Control     DCD--> DTR--> ---+|
>           Transmit Data                      RxD--> TxD--> --+||
>                    Ground                    GND--- GND--- -+|||
>                                                             ||||
>                    Ground                    GND--- GND--- -+|||
>           Receive  Data                      TxD<-- RxD<-- --+||
>           Receive  Primary Modem Control     DTR<-- DCD<-- ---+|
>           Receive  Secondary Modem Control   RTS<-- CTS<-- ----+
>
>       The obvious bilateral symmetry here maps nicely to an 8-conductor
>       RJ-45 flat cable: one side of the cable transmits in one
>       direction, the other side in the other direction.

An interesting proposal, but someone beat you to it!  I have here a
"Wyse-995 Multiport Adaptor" (bound to be a trademark or three in
there somewhere!) which provides 8 RJ-11 sockets on a plug-in AT card.

The box also contains cables and adapters for RJ-11 <-> DB25 plugs.

They have decreed that their RJ-11 pin assignment is:

        Signal          Card            Adaptor         Signal
         Name            Pin     Cable    Pin            Name

         DCD               1 <------------- 6            DSR/DCD
         TXD               2 -------------> 5            TXD
         FG                3 -------------- 4            FG
         SG                4 -------------- 3            SG
         RXD               5 <------------- 2            RXD
         DTR               6 -------------> 1            DTR


The adaptor RJ-11 pins are brought out to DB-25 1/2/3/7/8/20.

A couple of comments: they have retained the frame ground line,
as well as signal ground (probably a good idea); and you lose the
pretty bilateral symmetry, but it's been replaced with another one...

So, it's a nice idea, but keep in mind that a commercial mob have
already got their own version out.  I can see it now, the RS-232
hassles all over again!

(Disclaimer - I don't work for WYSE, I don't plug their products etc)
And I don't think I've revealed any trade secrets...
-- 
Dave Horsfall  (VK2KFU)             ACSnet/CSNET: dave@astra.necisa.oz
NEC Information Systems Aust.       ARPA: dave%astra.necisa.oz@uunet.uu.net
3rd Floor, 99 Nicholson St          JANET: astra.necisa.oz!dave@ukc
St. Leonards NSW 2064  AUSTRALIA    UUCP: {enea,hplabs,mcvax,uunet,ukc}!\
TEL: +61 2 438-3544  FAX: 439-7036         munnari!astra.necisa.oz!dave