i've just got a sound city bass 150 amp head second hand, in really good condition, but i've got a problem. on the back i've got 2 speaker outputs (obviously) but theirs some other stuff on their and i don't know what it does. 1 the ohm selecter, i know what it does, there's 4, 8, and 16 ohms, but theirs something else called a 100 v line or something, what does this selection do? also theirs a thing called a slave in/ out, what does this do. i also have a 600 ohm output, anyone know what this does? lastly, theirs another output thing, it says something to do with a battery or radio, what does this do. the last three things don't have sockets on them but i can get them fitted, i just don't know what they do. can anyone help?