IBM 3101 Dip Switches Configuration

From: Ethan Dicks <>
Date: Sat Jan 26 00:36:08 2002

--- Dave McGuire <> wrote:
> On January 24, Doc wrote:
> > > The problem is that the IBM 3101 don't establish communication...
> >
> > If by "normal serial cable" you mean a standard port-to-modem cable,
> > that is most likely your problem. You need to use a null-modem serial
> > cable with a terminal.
> That depends *completely* on the terminal. Several even have both
> DTE- and DCE-wired connectors.

I've seen that on some 3rd party VT100 clones (CiTOH), but it was two
connections - one for host, one for external printer, or two hosts (with
a keyboard sequence to swap the active port) - one was a DB25F, the
other a DB25M, but only because the primary use for them was to act
like DTE on one and DCE on the other (the dual-login thing was obviously
a hack that got documented - not even VT100s could do that back in the
> My standard rule for dealing with an RS232 in-yer-face is to plug it
> in without a null modem and see if it works...if it doesn't, then plug
> in a null modem.

I either use a traffic light or my magic cable. I built it when I was 16.
I need to ohm it out someday, but it has the property of magically unhosing
serial connections that are hosed. It's not simply 2-3 and 3-2... there's
some handshaking swapping going on. I built it to hang off of my C-64
RS-232 cart and attach to a variety of things including an ancient EPROM
programmer. I've kept it because it's a magic cable that rarely lets me
down when a device needs more than just TXD and RXD.


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Received on Sat Jan 26 2002 - 00:36:08 GMT

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