I have a DSP4000 with version 2.00 software. I am trying to connect it to my Mac through a serial adapter (Keyspan USA-19HS) so that I can use it with VsigX. I have the Serial adapter connected to the 9-pin input of the DSP4000 (there is also an output). I looked through my printed manual but I don't see any mention of serial connections, though I see that others talk about it on this unit. Do I have an old DSP4000, or is there setting I'm missing?