Complex sentence: The belt is either laid out on the ground or suspended from a tree or wall, and the end of the fuse is lit. As the fuse burns, it ignites each of the explosives in turn at a rate of up to 1000 rounds per minute.
Split into simpler sentences: The belt is either laid out on the ground or suspended from something like a tree or wall. The end of the fuse is lit, and as the fuse burns, it ignites each of the explosives in turn at a rate of up to 1000 rounds per minute.