In a message to david about "hang", Paul said:

db> Didn't you say once before that someone dropping carrier caused
db> COM.SYS to hang the machine?  Maybe it's not COM/SIO, but really
db> your hardware?

PE> No.  COM.SYS gets *disabled*.  I can't use the "mode" command.
PE> Anthony knows more of the technical details if you need more info
PE> than that.

COM.SYS _deinstalls_ itself when someone drops carrier. Or at least,
that was what appeared to be happening when the problem last reared its
ugly head a few months back.  Any access to com ports thereafter
resulted in error messages that you'd get when an access was made to a
serial port when it wasn't actually there, that sort of thing.

I told Paul to use the COM.SYS switch that STOPs COM.SYS from
deinstalling itself if it gets more than 1000 'false' interrupts or
whatever it called them, but it didn't seem to fix the problem.  When he
installed SIO, the problem went away.  I'm not sure what he is using at
the moment.

'tnt, Amfony.                        
--- Maximus/2 2.01wb