I have an
EDI rack and the local high school has one as well, that both have
houselight control on a cable as described. On both these units there is a 15 vdc
power supply located in the back of the rack just above the multilink. It sends out the 15 volts on two of the wires in the DB
connector. The remote units themselves have a small solid state
switcher and a
circuit board with sliding variable resistors. On that
circuit board, there are adjustments to take the 15 vdc to 10 vdc and then the remaining wires are the
return of 0-10 analog control and some logic wiring allowing the
house control to be taken at several locations. Again in the back of rack where the
power supply is located, will be
circuit boards that take the 0 -10 analog and make a Pulse width modulated signal that in turn will operate the dimmers in the rack that have been wired for houselights. With
EDI, each rack and the number of control stations is customed wired. Somewhere there will be a set of schematics the size of
house blueprints. Both racks that I am refering to, are the MK-7 series. IF yours are MK-X then it probably will be quite different. The MK-7 is identifiable by six 4
channel modules running horizontally across each row, with a panel called a multilink, that will have a
patch panel all the way across, that uses what appear to be small staples, to determine which dimmers are controlled by 10 analog channels. These channels in some installations are called emergency channels, and in some others are used in a control station so that prepatched dimmers can be controlled by a set of faders mounted for the convenience of not having to use the main
console. Very popular in High Schools, so that for a band concert the main board does not have to be accessed. The MK-X has
plug in modules, with each module running horizontally the full width of the rack.
EDI keeps pretty good records of each install. If you have no luck with
EDI or school maintenance finding the documentation you need, let me know and I probably can help you out, with your schools permission.