Control/Dimming Adding LED Instrument to Existing Lighting Rig


New Member
Mar 19, 2016
Cambridge, MA
Hello all,

I am working in a space that has two portable 12-dimmer racks and I am trying to add an LED luminaire to the system.

I am using a computer program called Isadora, which I know quite well, and my Macbook Pro instead of the tiny control console that is in the space. I am interfacing it with the lighting system using a piece of hardware called an ENNTEC USB PRO Mk2, and have been able to successfully been able to control the system with my computer.

There are two portable 12-dimmer racks. They are ETC Sensor, Model # SP: 1220B (or 122OB?). I cannot find a manual or page for them online, probably because they are very old, (ETC is now on the third generation of their Sensor line).

The LED luminaire in question is Rosco/The Black Tank's new PICA Cube 4C
Link 1, 2, 3, Gen Manual, 4C Manual
The DMX input for this is Cat5/5e/6, so I have two sets of both male and female Cat5/5e/6 to DMX adaptors.
I have successfully controlled the PICA Cube on its own by plugging it directly into the ENTTEC.

My question:
Do I need a DMX Terminator even though everything seems to be working just fine?

I am not that familiar with the specifics of how to add LEDs to an existing system of dimmers. I gather that I should use a terminator, but I plugged the DMX from the PICA Cube into the "DMX Thru" on the terminal dimmer (and flipped the terminator switch on the back of it the rack from "On" to "Off"), and everything seems to be working fine without a terminator.

Any thoughts would be much appreciated.

Thanks in advance,



Well-Known Member
Feb 24, 2004
DFW, Tx.
I think the dimmers are 1220B, as in 12ch @20amp per channel. I doubt they're very old, since to us, very old dates back to the 50's, 60's or later. These are likely from the 90's or early 2000's meaning they're just getting broken in. Not that it matters much :).

As to your question, a terminator is a good idea but not always a requirement to have things work correctly. Some people will not have a system work correctly until a terminator is added, while others will run without terminators for years without a single hiccup, but they will save you from signal reflection issues which could happen at any time - so it's a good cheap insurance.


Well-Known Member
Sep 18, 2009
Spokane, WA the great "Inland Northwest"
As @Les says "cheap insurance" and keep in mind that things can change in a rig. So even if it's working now in may not continue, without a terminator.

Manuals and such for the rack are easiest to find by the processor type MPE (no beacon light) CEM (red light), CEM+ and CEM3 (blue lights) Fine points of the rack itself will take some more info, like which processor you have. The rack is probably listed as a "SP12" but ordered with all D20 modules (check all your dimmer types, over by the green indicators!) Those manuals are at When in doubt call ETC 800 688-4116 they can and will tell you anything you need to know!

The most common mistake with those new to LED fixtures is plugging them into dimmers. Don't! Not even one set to non-dim. Use one of the unswitched convenience outlets on the rack instead, or a relay module if you have one, or wall power if you have to.
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