un-dedicating a line to a dialer - (nf)

[brad at bradley.UUCP]

#R:lpi3230:-12600:bradley:3900006:000:942
bradley!brad    Jan  6 10:02:00 1984


Version: UNIX V7m 2.1
Modem: Hayes Smart

We use one of our lines for both in and out. The only way we did is via
a kernel hack, which I have not done (we are waiting for 2.9). But for
the time being we use a smilar method. In going from 1 -> 0 in the ttys
file when you try to 'open' the device the modem has not set the bit
which refers to carrier detect. In out version of UNIX a null line uses
the 'dm' potion of dh/dm insted of dh. What this means is it hangs the
open waiting for carrier. What we did, which is a bigger kludge, is go
from 1 -> 2, wait about 10-15 sec so as not to klobber init. then go
2 -> 0, and wait again. This asserts carrier on the line and allows to
dial out. Now when you hang up the phone you have to go back to 2
then go to 0 (waiting of course). This is a pain but we only talk to
three machines and are awaiting 2.9 so we can live with it.

Brad Smith, Bradley University
{ihnp4,cepu,uiucdcs}!bradley!brad