# The DMX termination plug



## McCready00 (Sep 21, 2008)

Is it still used in the industry? I just never seen someone using it so far. Is it because the news machines don't need it? If you are still using it... then when?

Thanks


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## Wolf (Sep 21, 2008)

I still like to use them. Some people feel that the risk of corrupt information coming back up the line is very slim and dont feel it is necessary to use them. While the chance is slim the one time you dont use them is the time that something will happen and you may spend 20 mins trouble shooting instead of programing. Although some manufactures do have built in terminators so that is not necessary to use them (most boards have them).


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## DaveySimps (Sep 21, 2008)

I still use them in all of my rigs. I also see them reguarly in touring productions with new gear.

~Dave


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## church (Sep 22, 2008)

I always use them, the problems are most likely to occur at the end of a long termination and/or when you are approaching the 32 unit load. This is when the DMX signal is approaching its minimum signal parameters. 

This is also why using an optically isolated DMX splitter improves the "reliability" of the command link - because it includes line drivers on the output you have the ability to drive another 32 units on each output.


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## Kelite (Sep 22, 2008)

McCready00 said:


> Is it still used in the industry? I just never seen someone using it so far. Is it because the news machines don't need it? If you are still using it... then when?
> 
> Thanks




When responding to Right Arm or Smart Color tech calls, a large percentage of DMX related misbehavior is traced to DMX termination (or lack of, in this case). Moving lights and color scroller PSU's rely upon a clean DMX signal though the entire run, and the longer the DMX run the more chance of reflection, as Church has pointed out.

DMX termination is very similar to car insurance. Sometimes you'll need the insurance when away from the system, and someone adds/subtracts/substitutes fixtures within your run. It seems rare that these changes are mentioned to the designer/TD/ME until a problem occurs...


This is a very valid observation, McCready00. I would stick with a DMX terminator at the end of each run.


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## icewolf08 (Sep 22, 2008)

You should always terminate your DMX lines as it is the proper way to run a DMX distribution system. I have seen plenty of unterminated DMX systems work fine, but at the same time you may not know if some internal motor is a fixtures is sitting there twitching because of reflected data. A terminator costs $5 and 5 minutes to build, so keep them in stock and use them, better safe than sorry.


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## rmarston (Sep 22, 2008)

I agree - DMX was developed to be a very robust data buss based on EIA 485. But that buss was designed to be terminated with a 120 ohm resistor. It's a simple to add a terminator to each DMX buss to prevent the possibility of reflected data screwing up any fixtures.

Rick


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## avkid (Sep 22, 2008)

icewolf08 said:


> A terminator costs $5


You're paying too much for parts!


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## zuixro (Sep 22, 2008)

avkid said:


> You're paying too much for parts!



Yeah, Mouser has the connectors for $2.68. The resistor is just a few cents.


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## derekleffew (Sep 22, 2008)

See the Glossary entry: http://www.controlbooth.com/forums/glossarys/8909-terminator-dmx.html?highlight=terminate.

Wolf said:


> ... Although some manufactures do have built in terminators so that is not necessary to use them (most boards have them).


This is an absolutely *UNTRUE* statement. By definition, the control console or DMX source *cannot* terminate the line. Some dimmer racks and devices have a termination *switch*. *I (and others) have yet to be shown a moving light or LED fixture that has "auto-termination" or "self-termination."* I cannot recall ever seeing a *fixture* with a termination switch.

McCready00, you might find this poll useful: http://www.controlbooth.com/forums/...inate-your-dmx-lines.html?highlight=terminate. "DO as we say, not as we do."


Kelite said:


> When responding to Right Arm or Smart Color tech calls, a large percentage of DMX related misbehavior is traced to DMX termination (or lack of, in this case).


Kelite, your manuals need some revision. In previously researching this topic, I found that the RightArm manual does have a one-line remark (with an error!), but could not find any mention of 5-pin termination in the SmartColor manual. See this post: http://www.controlbooth.com/forums/what-went-wrong/8895-dmx-decides-go-strike.html#post103731.


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## Malabaristo (Sep 22, 2008)

derekleffew said:


> *I (and others) have yet to be shown a moving light or LED fixture that has "auto-termination" or "self-termination."* I cannot recall ever seeing a *fixture* with a termination switch.



Actually, current models of the Source Four Revolution are self-terminating. There's a switch built into the female XLR that connects a termination resistor when nothing is plugged in. Here's a link to the manual. Page 4 is where that feature is described. Apparently they've been that way since at least the beginning of 2007.


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## derekleffew (Sep 22, 2008)

Thank you for the correction, Malabaristo. Are you aware of any other fixtures having this feature?http://www.controlbooth.com/forums/members/malabaristo.html


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## gafftaper (Sep 22, 2008)

EDI Scrimmer Sticks (portable dimmers) have a terminate switch on them. That's the only thing I've seen with one.


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## Malabaristo (Sep 22, 2008)

derekleffew said:


> Thank you for the correction, Malabaristo. Are you aware of any other fixtures having this feature?http://www.controlbooth.com/forums/members/malabaristo.html



Nope, that's the only one I've seen. Of course, ETC products are what I'm most familiar with, so that shouldn't be terribly surprising. As simple as it is, though, I'm sort of surprised it hasn't been a more popular feature. Especially since lack of termination is so frequently the cause of DMX problems.


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## gafftaper (Sep 22, 2008)

Malabaristo said:


> Nope, that's the only one I've seen. Of course, ETC products are what I'm most familiar with, so that shouldn't be terribly surprising. As simple as it is, though, I'm sort of surprised it hasn't been a more popular feature. Especially since lack of termination is so frequently the cause of DMX problems.



Seems like a really cheap and easy feature for manufacturers to install.


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## dannyn (Sep 22, 2008)

For how cheap they are, I do no see why you would not use one. If anything it gives you a piece of mind.


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## STEVETERRY (Sep 22, 2008)

Malabaristo said:


> Actually, current models of the Source Four Revolution are self-terminating. There's a switch built into the female XLR that connects a termination resistor when nothing is plugged in. Here's a link to the manual. Page 4 is where that feature is described. Apparently they've been that way since at least the beginning of 2007.



This is correct. I forgot that we implemented this in 2007. Moral of this story: never ask the VP of R&D about product details.


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## porkchop (Sep 22, 2008)

The tour I'm on doesn't even have a single terminator in stock. This drives me nuts if you ask me you should terminate every dmx run. Like we've illustrated they are cheap and often the misbehavior can be seem by people not looking for it. I have seen High End techno's that need to be terminated always, but I can't say that I've noticed any thing not working right with our current unterminated rig.


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## JD (Sep 23, 2008)

Anybody that has looked at the signal with & without on a scope will opt to terminate!


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## Blackfaer (Sep 25, 2008)

I can detect a noticeable difference when I take my terms off my units; my technobeams will occasionally bounce around as if receiving occasional incorrect settings. It's foolish not to use terminators if you are running anything more than a few feet from a splitter or console. 

I'm not familiar with any movers (I haven't used the Revolution) that have self-termination, but many dimmer systems have either a switch or they auto-terminate. I seem to recall that some of Wybron's color scroller power supplies self-terminate, but that might just be referring to the scroller data lines, not the actual DMX. I'm not sure.


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## derekleffew (Oct 26, 2008)

Malabaristo said:


> Nope, that's the only one I've seen. Of course, ETC products are what I'm most familiar with, so that shouldn't be terribly surprising. As simple as it is, though, I'm sort of surprised it hasn't been a more popular feature. Especially since lack of termination is so frequently the cause of DMX problems.


For anyone interested in building one's own DMX devices, here is the Neutrik spec sheet on the connector in question, as used on the ETC Revolution: Neutrik - Industrial - A Series - NC5FAV-SW.




The SmartPack uses this connector also, as evidenced in this statement:


> DMX may be daisy-chained from one panel to another utilizing the XLR connectors on the front of
> the unit. When daisy-chaining DMX, utilizing only the XLR connectors, the DMX-Thru connector is
> self terminated when no connection is made.


from this document: http://www.etcconnect.com/docs/docs_downloads/manuals/SmartPack_Portable_SetupGuide.pdf.


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## TimMiller (Oct 27, 2008)

personally i would prefer pushing a termination button or plugging in a terminator over relying on a fixture to self terminate. I would fear that something would eventually get corroded and the fixture would decide to terminate or not terminate when it should and with my luck i would have a fixture in the middle of the run decide to terminate itself on top of the fixture at the end being terminated and cause the entire data run to freak out due to there being two terminators on the line. If it can go wrong it eventually will. I still cant get over the time i had a data cable coming off of the first fixture decide to quit during the second song in a show. It had been working fine for the previous 2 days of programming.


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## GoboMan (May 21, 2013)

In addition to working in theatre, I also sideline as a mobile DJ during my non-theatre weekends. A while back I invested some money into four intelligent lights for my DJ setup. I bought four of them, and when I placed the order the salesperson on the other end "highly recommended" I also purchase a DMX terminator that would plug into the "out" DMX port on the final light in the daisy chain. He said that not using a terminator would cause addressing issues and could cause my lights to behave oddly. So I added the $29.99 to my order to buy the thing.

Last week I did a gig and when I got there I discovered that I had forgotten the terminator at home. Not having enough time to run home and get it, I set up my lights without the terminator attached and to my surprise the lights behaved just as they always have, and exactly as I had programmed them on my controller.

My question is... Is a DMX terminator on moving lights even necessary, or did I get tricked into spending more money?


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## DuckJordan (May 21, 2013)

It is because it will work without one until it doesn't. Although $30 for one is expensive.


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## derekleffew (May 21, 2013)

GoboMan said:


> ... My question is... Is a DMX terminator on moving lights even necessary, or did I get tricked into spending more money?


Yes, to both.
1. Doug Fleenor Design - Why Terminate?
2. You spent $29.99 for approx. $3.47 in parts.


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## techieman33 (May 21, 2013)

Sometimes they work and others they don't. You could go years without one with the same rig and never have a problem then one day need it when those weird problems show up. You did pay to much for it though, you can buy them for $10 on ebay, or make one very easily yourself with a bare dmx plug and a resistor.


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## GoboMan (May 21, 2013)

Darn, I really *did* overpay. Crap. Well, I guess I'll never buy anything else from that store again!


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## GoboMan (May 21, 2013)

Now that I think about it, there is no terminator on the final dimmer rack at my theatre. We don't have any moving lights, but we use two ETC Sensor dimmer racks. Would you advise that I put a terminator on the final dimmer rack?


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## DuckJordan (May 21, 2013)

It likely has a terminator switch built in.


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## Les (May 21, 2013)

No, I don't think that's necessary. The Sensor racks most likely have built in termination. I say that because never have I seen a terminator sticking out of a Sensor (or any) dimmer rack. Now dimmer packs are a different story in most cases.


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## techieman33 (May 21, 2013)

Some DMX devices are self terminating, you'll just have to check the manuals for each one and see if that's the case. It's usually higher end fixtures that will have it.


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## derekleffew (May 21, 2013)

techieman33 said:


> Some DMX devices are self terminating, you'll just have to check the manuals for each one and see if that's the case. It's usually higher end fixtures that will have it.


Care to name these alleged "self-terminating" fixtures?


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## DavidNorth (May 21, 2013)

ETC SmartPack [rackmount version] and later models of Revolution [labeled when fitted].

David


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## Kelite (May 21, 2013)

Using a DMX terminator is somewhat similar to wearing a seat belt (other than there are no laws about DMX termination, just recommendations). If, in the event of signal reflection due to wireless devices, faulty/worn cable, failing PCB components within a lighting fixture, etc., the signal will pass in only one direction and not 'bounce back' down the line. 
Imagine throwing tennis balls at a wall, and every so often a thrown tennis ball returns and strikes one which has just left your hand. This is similar to DMX reflection in an odd type of analogy. Now stick carpet tape all over the wall and resume throwing the tennis balls. These balls now stick to the wall, limiting the liklihood of them reflecting back and striking oncoming tennis balls.

I know, simplified explanation of a non-simple phenomenon but still somewhat effective in understanding reflected data.


Go in peace, terminating as recommended-


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## sk8rsdad (May 21, 2013)

derekleffew said:


> Care to name these alleged "self-terminating" fixtures?


ETC Selador Desire D40 and D60 self-terminate, except for the XT variants. I suspect the Source Four LED uses the same parts but haven't checked the manual.
http://www.etcconnect.com/docs/docs...dor_Desire_Series_v1.4.0_User_Manual_RevA.pdf


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## DavidNorth (May 21, 2013)

sk8rsdad said:


> I suspect the Source Four LED uses the same parts but haven't checked the manual.



Indeed, the Source Four LED is self-terminating. Thanks for adding those....you'd think I'd know that. Ugh.

We've been through this discussion before, as I am reminded. A couple of points....

- Self-terminating connectors are available from Neutrik
- These connectors were co-developed with ETC
- They are not cheap, which is likely why not many manufacturers use them
- They disconnect termination when a male is plugged into the pass through female
- If you get in the habit of always using terminators, it doesn't matter whether products are self-terminated or not
- Having a termination switch available on the product is not the definition of self-terminated, but is appreciated when termination at end-of-line is needed
- Terminators never create problems, unless there is a wiring issue or receiver chip failing
- Many systems run fine without termintors everyday, BUT!!!
- Control problems can, and do, occur without warning even after minutes, days or years of working without issue.

Terminators are your friend [not the movie kind].

David


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## MiltonDavis (May 21, 2013)

David North stated the facts about terminators very well. In addition, I can add a couple of other points:

- Any system that works without a terminator, but "breaks" with one installed is a system that should not be able to operate at all. The terminator is just showing up the problem. It's only works without the terminator because you are lucky. [Edit by mod: see the thread http://www.controlbooth.com/threads...terminator-was-the-problem.28635/#post-254583 .]

- $20 for a terminator isn't necessarily a ripoff. If it's just a tin plated 5 pin XLR with a 120 ohm 1/4W resistor inside, then yes, that's a bit expensive. However, if the connector has gold pins, a proper 1/2W (or larger) resistor and good marking, $20 isn't out of the question. If you add other features like surge protection, the price can go higher still.

- The practice of termination is called out in the EIA/TIA-485 electrical standard. This is the electrical standard on which DMX512 is based. (just an interesting factoid).


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## sk8rsdad (May 21, 2013)

DavidNorth said:


> Indeed, the Source Four LED is self-terminating. Thanks for adding those....you'd think I'd know that. Ugh.
> David



It didn't show up in the user manual until a fairly recent edition, which is why I bought a bunch of terminators when we purchased our D40s over a year ago.


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## JD (May 21, 2013)

As for paying $29.95 for a terminator, I wouldn't waste $20 worth of time worrying about it! Just keep it in the back of your mind and double check prices this vendor charges on future purchases. 

Some terminators do cost more and may actually have other parts in them (such as 5 volt MOV's between each signal pin and pin 1) but the only part required by the standard is the resistor between pins 2 and 3.


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