difference between ph1 and tty000

[Bob Sanderman]

I'm trying to capture data coming into a 7300 via modem.
The following command works fine when I have a 1200 baud modem
attached to tty000:

(stty 1200; cat > /tmp/data) < /dev/tty000

When I run this the cat command will wait until the modem answers
and all data is transmitted before exiting.

If I change /dev/tty000 to /dev/ph1 the cat immediately returns
without waiting for any data or even the modem to answer a call.

How can I get /dev/ph1 to work?

Thanks
Bob Sanderman
att!mhuxu!rs