This unit allows up to 4 pairs of speakers to be connected to a hifi system, with its easy to use spring clip terminals. The switch on the front allows for easy control of either sets of speakers, or both. So you just run four sets of speakers into this box, then one set of cables from box to the speakers terminals on the amplifier (or hi-fi). Then you can switch between all sets of speakers, or all at once. Great for having music in more than one room.