I am ot sure if I had time to look at it but it seems that standard serial connections for cable replacement requires 2 units.
Whereas astronomy gear may require programming. I must admit there is not a lot of infomration I can use in the web, the application data suggests 2 units for serial cable replacement. Astronomy mounts seem to suggest a single program
http://www.astromist.com/
That is the best i can do.