Jeff Bosch wrote: > does the software have to be low level? > > thanks, > jeff bosch Yes, if your objective is to set/reset and read the link lines under program control. I believe the Mac serial port driver does not provide this kind of access to the CTS/DTR lines. In any case, there are not enough lines to make this work - you need two inputs and two outputs for a link interface. This is true for _standard_ Mac hardware.