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From: hope@gatech.CSNET (Theodore Hope)
Newsgroups: net.micro.att
Subject: 3b2 pins: here it is
Message-ID: <3155@gatech.CSNET>
Date: Sat, 29-Mar-86 15:46:08 EST
Article-I.D.: gatech.3155
Posted: Sat Mar 29 15:46:08 1986
Date-Received: Sun, 30-Mar-86 10:47:13 EST
Organization: School of Information and Computer Science, Georgia Tech, Atlanta
Lines: 61

Someone posted this a long time ago, and I saved it.  Here it is:

-------

These are the ACTUAL pinouts of the 3B2's strange 8-pin modular RS232
connector, and all the known flavors of TRW modular-to-DB25 adapter (part
number 232-21-25-xxx) for the 3B2, determined by inspection.
It seems they did quite a bit of hacking to disguise the lack of a DSR pin.
Note that the modular-modular CABLES supplied with the 3B2 are crossed over
(1->8, 2->7, etc.) and the tables below assume the use of such a cable.
Also note the adapter pinout list in the Appendix of the 3B2 Owner/Operator's
manual is WRONG!!
Yes, the male and female "Terminal/Printer" connectors are DIFFERENT.

				 DB25 PINOUTS (see below for abbreviations)
					#010	#006	#008	#005
3B2		       3B2		Male	Female	Male	Male
MODULAR		receives  sends		Term./	Term./	Remote/	ACU/
PINOUTS					Printer	Printer	Console	Modem
--------	-------- --------	-----	-----	-----	-----
1 "Prot.Grd."				1 FG	1 FG	1 FG	1 FG
2 "Reserved"(CTS)  <--			4 RTS	4 RTS	5 CTS	5 CTS
3 "TXDO"	   <--			3 RxD	3 RxD	2 TxD	2 TxD

4 "DTRO"	   <--			8 DCD	8 DCD	6 DSR,	20 DTR
							20 DTR
							      |
5 "RXDO"		  -->		2 TxD	2 TxD	3 RxD |	3 RxD
							      |
6 "DCDO"		  -->		6 DSR,	6 DSR	6 DSR,|	8 DCD
					20 DTR		20 DTR

7 "Signal Grd."				7 SG	7 SG	7 SG	7 SG
8 "Reserved"(RTS)	  -->		5 CTS	5 CTS	4 RTS	4 RTS

---------------------------------------------------------------------

DB25	RS-232-C "Standard" :-)
PIN	ABBR.	NAME			DIRECTION
----	----	----			--------------
1	FG	Frame Ground		      --
2	TxD	Transmit Data			to DCE
3	RxD	Receive Data		to DTE
4	RTS	Request to Send			to DCE
5	CTS	Clear to Send		to DTE
6	DSR	Data Set Ready		to DTE
7	SG	Signal Ground		      --
8	DCD	Carrier Detect		to DTE
20	DTR	Data Terminal Ready		to DCE

--------

Caveat Emptor:
There are two versions of plugs distributed with 3b2 equipment: the males
with a '232-21-25-010' and the males with a '232-21-25-007' part number.
Their pinouts are not the same!!!!
-- 
Theodore Hope
School of Information & Computer Science, Georgia Tech, Atlanta GA 30332
CSNet:	hope@gatech		ARPA:	Hope%GATech.CSNet @ CSNet-Relay.ARPA
uucp:	...!{akgua,allegra,amd,hplabs,ihnp4,seismo,ut-sally}!gatech!hope