Quick breakdown of the three:
Channel:
There are two parts to this answer. Usually the position on the board. So, you may have a 24
channel board, the first control would be called
Channel 1. (In
conventional dimmer systems.) Most boards and systems these days are
DMX, so there is a twist: Most boards allow output soft patching, so board
channel #1 could actually be patched to any
DMX channel(s). Lets assume it is patched to
DMX channel 1.
Dimmer:
The workhorse. Most
DMX dimmers can also be soft patched at the
stage. If you have a 12
channel dimmer pack, you set a starting
address and for example if that is number 1, than
dimmer #1 is running off
DMX #1, which is running off board
channel #1. if you soft-patched as a
block, then 2 to 12 would also be
DMX/board channels 2 to 12. Now, here is the beauty of
DMX, if your
dimmer is 2.4k per
channel, and you need six 1000
watt lights on that
channel, you can program multiple
dimmer channels onto one board
channel. In this case, three dimmers could be programmed on
DMX #1 with two of the lights on each
dimmer. Most packs will allow all 12 channels to be soft-patched to any
DMX channel, so your 12 x 2 pack can also be a 6 x 4, or for that matter a 1 x 24k pack.
Circuit:
Usually refers to the limited
power branch that comes off of the
dimmer pack. So, we might
call dimmer #1
circuit #1. In the above example where we are running 3 dimmers off of one
DMX channel, the outputs of those dimmers would still be 3 circuits each with a 2.4k limit, even thought we have a total of 6k of lights running off of it.
All of these terms are left over from the days when the
dimmer system was a big cage full of autotransformer dimmers (or resistance plates if you are really really old!) and running lights required one to work out with weights first! Back then, the big handle to the top and left was
dimmer #1, and the four
circuit breakers that broke it down to 20 amp circuits (not always) were known as circuits 1A, 1B, 1C, & 1D. (At least until you got to the
hot-patch bay, otherwise known as the death board!) The
introduction of modern systems with multiple levels of soft patch have made things a little more confusing!