Xref: utzoo comp.periphs:650 comp.terminals:509
Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!laidbak!zog
From: zog@laidbak.UUCP (Christian G. Herzog)
Newsgroups: comp.periphs,comp.terminals
Subject: Re: Help -- Making a modem with DB9 connector --> DB25
Keywords: US Robotics modem DB9 DB25
Message-ID: <1279@laidbak.UUCP>
Date: 13 Dec 87 05:30:20 GMT
References: <860@seradg.Dayton.NCR.COM> <3150@batcomputer.tn.cornell.edu> <4299@ecsvax.UUCP>
Reply-To: zog@laidbak.UUCP (Christian G. Herzog)
Organization: LAI Chicago
Lines: 45

The original question was related to a particular type of USR modems
and was not really a generic 9->25 pin adaptor question (even though the
article which contained the wiring setups for the AT-style connectors is
a really excellent reference to keep around for those occasions):

The problem here is that the DB9 on the Password modems IS NOT an AT-style
connector.  The DB9 was intended to connect to an Osborne-1 which was designed
to use TTL rather than RS232 signal levels to communicate with the modem.

The Password series modems were all the same but came with enough pins on the
inside connector to allow both a straight TTL I/O (bypassing the line drivers
and receivers which perform the logic translation) rather than the more
conventional +/- 12 volt RS232 levels.

From the 12 pin header INSIDE the modem to an outside RS232 connection should
be as follows for the Password/Courier modems:

Connector:

	1 |	Unused
	2 |	"
	3 |	"
	4 |	pin 3 (on a DB25)
	5 |	pin 7
	6 |	pin 6
	7 |	pin 12
	8 |	pin 22
	9 |	pin 8
	10|	pin 5
	11|	pin 2
	12|	pin 20
	  ^
	  ^
	This is the ridge on the connector which allows the mating connector
	to plug in with the correct orientation.


							 __  __________  __
							|  ||_______   ||__|
	    Christian G. Herzog				|  | _______|  | __
							|  ||   ____   ||  |
          {ihnp4,sun}!laidbak!zog			|  ||  |____|  ||  |
							|  ||__________||  |
          Lachman Associates, Inc.			|  |___________ |  |
							|______________||__|