Selecting the correct Connection.
Make sure that you select an adapter that will be supported by your current PC. If you do not have a serial connector then do not purchase a Serial Adapter. If you have plans to go wireless in the future, select the USB485B. Also be aware that in a future release of software Light-O-Rama will support interaction from the folks viewing the display. If you plan to use that feature  you will also need the USB485B. If you are going to have a basic, computer controlled system that is connected using wires then you select the SC485 or USB485 as noted below.
SC485 Serial Adapter  Should be used with older machines with slower processors and a serial port. PC must be located within 100' of the first controller. Will not provide the power for wireless units. 
USB485 USB Adapter  Should used with new machines with faster processors. PC may be located up to 4000' from the first controller. Will not provide the power for wireless units.
USB485B USB Adapter  Best unit. Should used with new machines with faster processors. PC may be located up to 4000' from the first controller. This processor will provide the power for wireless units. It is the choice if you plan to have interactive shows in the future.
Wireless  Wireless gives you a nice alternative to hardwired connections. The wireless system will allow you to control your show from your PC without running a wire out of the house. (The wireless selection comes with two wireless units and a USB485B. )