> I've been trying without success to talk to the serial ports on my 
> SE/30...well, actually, to enable logins via them, but any kind of 
> communication would be great to start.  I connected a 2400 bps modem up 
> to it, to see what would happen, and all that happened was that the 
> lights on the modem flashed incessantly for about five minutes, then the 
> system complained "invalid login" from that port, and the lights stopped 
> flashing. I have no way of finding out what happened there, because when 
> I tried connecting a computer to the port and setting it to the same 
> settings (2400 bps, N81 and XON-XOFF flow control) I didn't receive 
> anything.  Should I be able to address the serial ports or not?

My best guess is that you don't have your /etc/ttys file set up correctly.
Default speed is 9600bps, I think.  I used to use my wife's T3400 (Toshiba
486 subnotebook) as a terminal, connected to tty01 (printer port) via
Mac-to-modem cable, a hand-made null modem adapter, and a 9-25pin serial
cable.  That worked fine.

You have to change the line below in /etc/ttys:

tty01   "/etc/getty std.9600" unknown     off secure

to something like:

tty01   "/etc/getty std.2400" vt100     on

(if you're using the modem port, read "tty01" as "tty00")

I copied the line above from a DECstation 5900 running Ultrix, so there
may be slight difference with the actual /etc/ttys content of your box.

Hope this helps,

Ken