We use Parallels for the navigation programs on our boat. There are two pieces of equipment that have serial connection cables that need to be working at the same time ( it's for sending emails through our Single Sideband radio. One serial for the Pactor digital modem and a second one for the frequency control cable on the SSB ) I've tried using 2 Keyspan single adaptors but have had a lot of trouble getting them both to work at the same time which is necessary to send emails without a lot of extra steps. Which is the best or most compatible USB to 2 - RS232 (serial) plug adaptor. I've found three One is the IOGEAR GUC2322 but has some bad reviews. The second is made by USBGEAR Part # USBG-232FT-1 A third is a VSCOM part # XC-232-C Any help appreciated. Digital high frequency email through a SSB (ham radio) is the only communication we have while at sea. Daniely website www.svtropicaldance.net