Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!philmtl!philabs!ttidca!hollombe
From: hollombe@ttidca.TTI.COM (The Polymath)
Newsgroups: comp.sys.next
Subject: Re: Solution to Apple Laserwriter Plus
Message-ID: <5637@ttidca.TTI.COM>
Date: 25 Aug 89 18:53:27 GMT
References: <19278@usc.edu> <246300047@uxa.cso.uiuc.edu>
Reply-To: hollombe@ttidcb.tti.com (The Polymath)
Organization: The Cat Factory
Lines: 31

In article <246300047@uxa.cso.uiuc.edu> jpd00964@uxa.cso.uiuc.edu writes:
}
}[null - modem cables]
}
}I believe that the following is correct, but I would not testify to it.
}
}Computers and terminals are considered terminals in RS-232 terminology while
}modems are considered computers.

Modems are pretty consistent about this.  They're nearly always DCE (Data
Communications Equipment).  Personal computers and their serial ports, on
the other hand, are more subject to the whims of the manufacturer.  My old
Osborne 1, for example, needs a null modem to talk to a modem through its
serial port.  So does my SO's PS/2.  This allows them to talk to DTE (Data
Terminal Equipment) serial printers _without_ a null modem. (Why this was
assumed to be the more common case, I don't know.  Both our printers use
the Centronics parallel ports).

}... To fix, use a
}modem with two wires switched and call it a null-modem.  ...

A null modem is a _cable_ with the data lines crossed, among other things.
(A true null modem cable crosses a few other things as well.  I've got a
complete pin-out, but it's easier to just buy one these days -- about $7
at Radio Shack for a null-modem-in-a-DB25-jacket).

-- 
The Polymath (aka: Jerry Hollombe, hollombe@ttidca.tti.com)  Illegitimati Nil
Citicorp(+)TTI                                                 Carborundum
3100 Ocean Park Blvd.   (213) 452-9191, x2483
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