The NES Satellite is an accessory for the Nintendo Entertainment System. Like the NES Four Score accessory, the NES Satellite also allowed four players to plug in to the same game. But, unlike the Four Score, the Satellite was also wireless, allowing players to sit up to 20 feet away from the Nintendo console.
The smaller unit plugs into the controller ports on the front of the NES and connects with the larger unit via an infrared signal. And, similar to the Wii, the line of sight between the two can't be broken or it won't work. The four controllers are then plugged into the larger unit.