Control multiple VTR from one Mac
SerialCommander is a single USB interface to four independent RS422 ports, communication unit. It is a small form factor box that you connect in USB to your Mac and it will add 4 RS422 serial ports on your Mac. The main use for that is to control multiple VTRs on one Mac, in order to record from them using MovieRecorder.
If you own an M|80 for example, with 2 SerialCommanders, you can control 8 VTRs on one Mac. This is ideal if you have a large library of tapes that you want to digitise. You will be able to capture from 8 VTRs at once, using just one Mac.