Xref: utzoo unix-pc.general:459 comp.sys.att:2759
Path: utzoo!utgpu!water!watmath!uunet!umix!mailrus!ames!zorch!pacbell!gladys!bakerst!cgh!manta!brant
From: brant@manta.UUCP (Brant Cheikes)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: Ways of connecting Unix PC's
Message-ID: <341@manta.UUCP>
Date: 9 Mar 88 23:06:55 GMT
References: <234@safari.UUCP>
Reply-To: brant@manta.UUCP (Brant Cheikes)
Distribution: unix-pc
Organization: Soul of the Gnu Machine, Philadelphia
Lines: 32

In article <234@safari.UUCP> dave@safari.UUCP (dave munroe) writes:
>I have a 3B1 and a 7300 which are connected to each other and the outside
>world [...]
>is it possible to take some of that neat RJ11
>cable and heads and make a "null modem" connection between the phone ports
>of the two machines to give me this:
>        7300                                   3B1
>    |       ph0<-----RJ11 null-modem------------->ph0|
>    |       ph1<  (unused)                 |      ph1<--(phone line)--->
>    |     rs232<-- printer         tty ---->rs232    |

From the above diagram, it appears that you hope to use both ph0/ph1
on the 3b1 for DATA connections.  As far as I can tell, this is not
possible.

In order for the 3b1's ph1 to be used for DATA, you must have set up
the 3b1 in a two phone line configuration.  This causes ph0 to become
a VOICE line.

One restriction I've noticed (and oft lamented) is that a 3b1 in a two
line configuration can NEVER use ph0 for DATA calls.  In F/S 3.51, the
phtoggle routine allows you to switch ph1 between DATA and VOICE, but
there does not appear to be a way to set both lines to DATA, nor a way
to make ph0 DATA and ph1 VOICE.  This is clearly because there is only
one modem chip, and it cannot be shared between two phone lines.  The
7300's one line configuration allows ph0 to switch between VOICE and
DATA, so from that end everything's ok.
-- 
Brant Cheikes
University of Pennsylvania
Department of Computer and Information Science
ARPA: brant@linc.cis.upenn.edu, UUCP: ...drexel!manta!brant