Control/Dimming Questions about CMX

Canadian.girl

Member
Joined
Apr 20, 2020
Location
Stratford Ontario
Hi! I'm currently a student for theatre production. I'm working on a slide show for my networking class and I'm having some difficulty with CMX. My first issue is what is the topology for the network? I haven't found much but I think it's a bus? Am I correct?

How is the signal structured for this network? I've been able to find its history and protocol but this has been an issue for me too find. Lastly why else is this no longer used as much? Is it because of how easily it's converted into DMX? Making it faster network to use?

If I'm wrong about anything or everything please let me know!! I've been struggling with this class all semester and I just want to understand and not fail lol.

Thanks!!
 

RonHebbard

Well-Known Member
Premium Member
Joined
Jun 12, 2004
Location
Waterdown, ON, CA
Hi! I'm currently a student for theatre production. I'm working on a slide show for my networking class and I'm having some difficulty with CMX. My first issue is what is the topology for the network? I haven't found much but I think it's a bus? Am I correct?

How is the signal structured for this network? I've been able to find its history and protocol but this has been an issue for me to find. Lastly why else is this no longer used as much? Is it because of how easily it's converted into DMX? Making it a faster network to use?

If I'm wrong about anything or everything please let me know!! I've been struggling with this class all semester and I just want to understand and not fail lol.

Thanks!!
Good morning @Canadian.girl
While you're waiting for a few of our 'better versed' posters to reply, I'll contribute a few points to ponder from the POV of a few starting points to delve into.
In totally random order:
In a sense, very similar to DMX (Essentially think of it as Colortran's variant of DMX).
While Colortran was still an entity (designing, promoting, marketing, commissioning, installing, supporting and maintaining) a range of products: Manual and / or memory control consoles, dimmer packs and racks. [ along with a range of incandescent ellipsoidals, Fresnels, Cyc' washes, et al ] THEIR consoles communicated with THEIR dimmers via THEIR CMX control protocol variant.

Once a number of their dimmer racks failed in a variety of undesired spectacular blazes of glory (Notably in Disney Land and / or Disney World) they were essentially sued into bankruptcy / out of existence and figuratively 'black balled' from virtually all installations of any appreciable monetary value and / or marketable significance.

(In your own town, I don't believe any of your Festival's original three venues [Festival, Avon, and Tom Patterson (or the TeePee if you prefer) ] have EVER utilized any Colortran controllers and / or dimmers of any kind; ask the Festival's Alec Cooper and / or the TeePee's Tim Hanson who've been with the Festival since the very early 1970's in Alec's case, 1977 in Tim Hanson's case AND are still employed there to this instant (within the contsraints of our current Corona mania / pandemonium)
That was basically the end of Colortran and their CMX variant / control protocol.

Big print in UPPER CASE: REMEMBER, you're merely reading the ramblings of some old retired geezer on the world wide web, thus don't quote any of this verbatim on your term papers; read my scribbles purely as potential points to have Mrs. Google ponder while you're trapped by our current Corona mania.
All the best from a long retired fellow Canadian.
Toodleoo!
Ron Hebbard
 
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STEVETERRY

Well-Known Member
Joined
Aug 12, 2007
Location
New York
Colortran protocol (CMX) and DMX512 are functionally similar except for speed. They both follow the RS-422 (now EIA-485) electrical standard for balanced-line transmitters and receivers. CMX operated at 153.6 kilobits per second (kbps), while DMX512 operates at 250 kbps. Some Colortran products like the Dimension 192 dimmer system could be converted from CMX to DMX512 with a relatively simple hardware change. Other products may require the use of an active converter, which is available from multiple manufacturers.

ST
 

microstar

Well-Known Member
Joined
Jan 19, 2014
Location
Lawton, OK
Good morning @Canadian.girl
While you're waiting for a few of our 'better versed' posters to reply, I'll contribute a few points to ponder from the POV of a few starting points to delve into.
In totally random order:
In a sense, very similar to DMX (Essentially think of it as Colortran's variant of DMX).
While Colortran was still an entity (designing, promoting, marketing, commissioning, installing, supporting and maintaining) a range of products: Manual and / or memory control consoles, dimmer packs and racks. [ along with a range of incandescent ellipsoidals, Fresnels, Cyc' washes, et al ] THEIR consoles communicated with THEIR dimmers via THEIR CMX control protocol variant.

Once a number of their dimmer racks failed in a variety of undesired spectacular blazes of glory (Notably in Disney Land and / or Disney World) they were essentially sued into bankruptcy / out of existence and figuratively 'black balled' from virtually all installations of any appreciable monetary value and / or marketable significance.

(In your own town, I don't believe any of your Festival's original three venues [Festival, Avon, and Tom Patterson (or the TeePee if you prefer) ] have EVER utilized any Colortran controllers and / or dimmers of any kind; ask the Festival's Alec Cooper and / or the TeePee's Tim Hanson who've been with the Festival since the very early 1970's in Alec's case, 1977 in Tim Hanson's case AND are still employed there to this instant (within the contsraints of our current Corona mania / pandemonium)
That was basically the end of Colortran and their CMX variant / control protocol.

Big print in UPPER CASE: REMEMBER, you're merely reading the ramblings of some old retired geezer on the world wide web, thus don't quote any of this verbatim on your term papers; read my scribbles purely as potential points to have Mrs. Google ponder while you're trapped by our current Corona mania.
All the best from a long retired fellow Canadian.
Toodleoo!
Ron Hebbard
In the book "Let There Be Light", in an interview with Robert Bell, David Cunningham (inventor of ENR) specifically states that the ENR's buss melting problem did NOT cause the Colortran bankruptcy (page 97). Interestingly, he paid for half of the dimmer rack buss bar retrofits that fixed the problem. However, it did cause ill-will between Cunningham and Colortran. Later, Cunningham and ETC won a big patent and royalty lawsuit against Colortran which basically bankrupted the company. Very interesting book.
 

Robert F Jarvis

Well-Known Member
Joined
Apr 8, 2017
Location
Sebring, FL, USA
Had a good look at a still-in-use Colortran system fitted in a local high school circa 1975. What a beast. The control console is a very solid piece of furniture. But ref the control signals": From what I could observe and measure it seemed that the console was sending a simple 0-12 volt dc signal (depending on the faders position) down to stage side to control the dimmers, rather than any "Data" packet protocols like DMX. Could be wrong here. But something to throw in the mix as I go stir crazy.
 

Robert F Jarvis

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Joined
Apr 8, 2017
Location
Sebring, FL, USA
That would fit in very nicely then with our findings. Several of the faders are stuck solid and of the main X fader pair one is out! The stage has a lot of tungsten lights arranged in banks so I think the only way these guys could go forward would be to use some newer dimmer packs and a very modest modern console to Wirelessly TX the DMX from FOH to stage. Woops - this is getting off thread my bad.
 

microstar

Well-Known Member
Joined
Jan 19, 2014
Location
Lawton, OK
That would fit in very nicely then with our findings. Several of the faders are stuck solid and of the main X fader pair one is out! The stage has a lot of tungsten lights arranged in banks so I think the only way these guys could go forward would be to use some newer dimmer packs and a very modest modern console to Wirelessly TX the DMX from FOH to stage. Woops - this is getting off thread my bad.
Pictures would be nice! I enjoy seeing/repairing the analog stuff.... great engineering in its day.
 

microstar

Well-Known Member
Joined
Jan 19, 2014
Location
Lawton, OK
So not including the houselight system, it's essentially an 15-channel console controlling 6 dimmers??? I wonder if the dimmer rack has slots wired for the additional dimmers since the patch panel is made for all 15? I've seen similar Berkey Colortran dimmer modules on Ebay.
The 3 houselights control faders and dimmers are probably totally independent of the preset/crosssfader since they don't show up on the bottom preset.
Yeah that split cross fader looks like the throttle controls on an airliner and the keyswitch something out of a nuclear power plant!
frntPanel.JPG chassisfFRNT.JPG nameplate.JPG
 

RonHebbard

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Premium Member
Joined
Jun 12, 2004
Location
Waterdown, ON, CA
1971-1975 - I remember just about every show but especially the details of the equipment and systems. I remember all my high school shows (almost) and every teacher since first grade.
Not to pull your leg TOO hard; only a little. . .
Like you; I've similar memories of long ago, I'm decent on last month....
Can you recall what you had for lunch the day before yesterday?
 
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microstar

Well-Known Member
Joined
Jan 19, 2014
Location
Lawton, OK
I interpreted 6 6Ks and 3 3ks and 6 more 3ks were VEd out or planned for future addition. Very common. My college had space for 30 3ks, 30 sliders in each preset, 30 sets of jacks on the patch panel, and only 21 (mag amp) 3ks. 50+ years after they built that they built an entirely new PAC.
I understand Value Engineering... the school I retired from had a 1978 install of 144 circuits in a dimmer-per-circuit configuration with Electro Controls bolt-in style dimmers.
The catch was we only had about 70 dimmers. If you needed to use a circuit without a dimmer, you had to remove a dimmer from somewhere else and install it.
A "future dimmer rack" location complete with conduit for 3-phase feed and load circuits was even provided to expand the system. Today the system is actually dimmer per circuit with ETC Sensor dimming and Ion control.