> > If I do an "echo ath1 > /dev/ttya" or an "stty all < /dev/ttya" (to
> > check the tty settings), it just hangs and I have to kill the
> > process.
> I had exactly the same problem when using my Sun 3/60 with SunOS 4.1.1 
> with my 14k4 modem. It turned out to be the Carrier Detect which was
> the problem: if you don't connect it at all everything works allright,
> but when it's connected to your modem, you'll only be able to write to
> the serial port when the Carrier Detect is high, which is really 
> troublesome with modems because most applications expect Carrier Detect 
> to be high only when a connection has been established.

In SunOS, you are supposed to use a different device (minor number) to
ignore CD.  In SunOS 3.5 (and I think 4.1 is similar) the devices are:

crw-rw-rw-  1 root     wheel     12, 128 Oct 22 18:28 cua0
crw-rw-rw-  1 root     wheel     12, 129 May 17 04:03 cua1
crw-rw-rw-  1 root     wheel     12,   0 May 16 22:13 ttyd0
crw-rw-rw-  1 root     wheel     12,   1 May 16 22:13 ttyd1

The cua? are used for outdial -- the open succeeds regardless
of CD.  The ttyd? are used for indial -- the open waits for CD.
I imagine NetBSD-sun3 has a similar capability.