After a lot of experimenting.
I've found using mdmbuf and ctsrts cu works fine with modems configured 
to default (at&f). ie CD is used as normal.  

ie
tty01   "/usr/libexec/getty comline.38400" rtscts mdmbuf off 

shell>ttyflags tty01 (or just ttyflags -a )


For dial in I use just ctsrts, but cu doesn't work work, without mdmbuf or 
CD forced high.

 Why not mdmbuf on it's own, it don't work too well all the time.

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James L Vodanovich                      jim@arrakis.com.au 
Arrakis Internet Services               http://www.arrakis.com.au/
Sydney Australia                        ph +61 2 310 7500