We have D20 dimmers on our Sensor SR48 rack. This 20 is supposed to mean 20 amps, but I am not sure if this is for the whole module, or the 2 channels on the module. Which is it? And is it just given that it is at 120V, or is voltage specified somewhere? (the rack gives a range of voltages that it will take...I think...from last time I looked.) Also, how are all the modules and the rack hookep up? I'm pretty sure the modules just slide in. Are there eleventy billion wires in the back to connect to the electrics? (do they have connectors on them?) Also, since our circuits repeat on the batten, are there just 2 plugs going to the same dimmer module, or are the wires parallel circuited in the drop box...? Also, there has been a lot of advice given on bench focusing, but (you can call me stupid) I am not exactly sure what that is, and have not been able to find the answer. Is this just focusing the bulb to match the focal point of the reflector? Should this be done with every new bulb? What is the difference between the 2 knobs on the back. (On a S4. The inside knob, and the outside knob.) I have read a lot about how to set up the fixture on a boom, and point it at the cyc, but I don't know what to do to the fixture. You guys rock.