rb:

It basically defines the base functionality of the machine. The various types determine what the speakers are that it will support.

Surround Music Fan/Computer Geek/Curmudgeon in training.
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861v4, HD621, Panasonic BD-P55K, Toshiba HD-A35, Oppo HD990, Dish Network 622, Pioneer DV-668AV-S w/ DVD Upgrades mod, EW Fontaine II (x5), Velodyne DD-15 (x2), Seymour AV Ice blocks (x7)