RDM ?

You are correct in thinking RDM isn't related to using the ETCPad. ETCPad only uses the network to talk back and forth.

RDM is basically an extension to DMX that allows bi-directional communication. It allows you to do things like set address of your fixtures and see error status of your dimmers. In order for RDM to work, your devices have to support it. I'd read up on what you have and if they support any RDM features. If your equipment doesn't support it, it's better to leave RDM unchecked.

Great, thank you. Though the chance of us being anywhere near using > 1 Universe are very remote I would still like to learn more about the very big shows that use DMX over Ethernet (Art-Net, sACN) and how some programs actually go out and 'find' node addresses. But how it ties in with local DMX is out of my ball park presently. Could you recommend any good books or on-line resources that start simply but go on to complex show systems?

I'm more of a YouTube kinda guy, so I can't suggest any good books. But to put it in the simplest terms possible as far as flow goes:

(optional), [description]

Old school:

Console -> DMX Cable -> (OptoSplitter -> Wireless DMX Trasmitter -> Wireless DMX Reciever -> DMX Cable ->) DMX Controlled Device

New school:

Console- > Ethernet -> (Ethernet Switch ->) Node/Gateway(s)[possible to get 1 or many universes through Protocols such as Art-net, sACN, EDMX..] -> (Wireless DMX Reciever -> Wireless DMX Transmitter ->) DMX Cable -> DMX Controlled Device

Search any of the terms here you don't understand yet in Google, and you get a heap of resources. After that, it is up to you to find one you can digest. After all, everyone has different learning styles. A good word I throw in front of my google searches if I'm having trouble grasping the concepts is "Understanding". So for RDM I would try "Understanding RDM Lighting" as my search and that would get me a few videos and a few articles to have a go with.

The best part about all the questions you have had so far is they all based on protocols. Protocols have a defined set of rules they have to follow to qualify, which makes for some pretty consistent learning materials.

Good luck!

This stuff is really a lot simpler than a lot of the jargon and complex explanations make it seem.

Normal DMX sends a stream of 512 bytes of data over a pair of wires each byte is a dmx address and the value of each byte can be from 0 to 255

sACN and Art-Net  simple send the same 512 bytes of data over an IP connection.   On the front of the 512 bytes there is an extra couple of bytes that can contain a universe number.

In simple terms the device that converts from sACN or Art-Net to DMX, spots the universe its interested in in the IP packets coming over the network, grabs the 512 bytes out of it and puts them out onto the DMX cable.

As others have said RDM is info comming back from the fixture or dimmer rack that's sent like DMX data but the other direction.

You almost dont need to know more than that for most usages

Thank you. I kind of assumed RDM was on the Ethernet cables. The fact RDM uses the DMX cables was a surprise. It is quite a nifty scheme with its backward compatibly. With your answer and others here plus an excellent "RDM (Lighting)" article on Wikipedia learned a lot in just a few hours. As said there is no chance of us as a small theatre moving beyond a single DMX universe in the foreseeable future but that doesn't stop one's interest in the subject. And yep - I see no point in leaving RDM on, in our Network setup.

You maybe surprised how quickly you can use up a universe!!

Even basic moving heads will take 16 addresses

LED Pars 6 to 8

LED Profile spot 9

So 30 conventionals, 20 LED Pars, 8 Profiles and 14 movers and you are almost out.   Add in some haze, laptop presentation control via dmx, and someone that wants to stick in a $45 32 channel LED strip controller and you are over by  23 addresses. 

You maybe surprised how quickly you can use up a universe!!

Even basic moving heads will take 16 addresses

LED Pars 6 to 8

LED Profile spot 9

So 30 conventionals, 20 LED Pars, 8 Profiles and 14 movers and you are almost out.   Add in some haze, laptop presentation control via dmx, and someone that wants to stick in a $45 32 channel LED strip controller and you are over by  23 addresses. 

Oh yes indeed no problems there. In our smaller Pavilion theatre we are using LED's and you're right. They are greedy little boogers. My emphasis on the simple nature of our main theatre is due to the fact a number of answers I received on connecting a ETCpad to an Element 2 through a Netgear WiFi router were a bit clouded by folks assuming we were running  a more exotic mix. Somewhere I saw a reference to a "smart" fixture that consumed 400 channels! What!