"OSI" Oh Shitt Insurance?
EDIT: Interesting; the site wouldn't let me post s h i t, it kept changing it to crap.
I've edited and learned the site accepts shitt.
"OSI" Oh Shitt Insurance?
Calling @bharrell Would you mind answering @almorton 's query?I'm not 100% sure but our Strand dimmer rack used to talk to our Strand 300 to report channel loading and so on (you could tell the desk to learn the loadings, then it would report channels that were abnormal), and I think it may have done that over the second pair, but I wouldn't swear to it.
Well, yes and no. You still need to follow the 300 ft. rule and don’t want to design an install that violates that with long cables, assuming gear is better to accommodate errors. I can think of bigger buildings that have to either do fiber or added switches.To pick up one point that DrewE and other commenters alluded to:
The reason that newer generation fixtures aren't limited to 31 devices on a link is that newer generation *silicon* isn't: this is equivalent to the reason why it's possible to go longer distances than the original spec says on Ethernet *on switched networks*. Before switches became ubiquitous, the distance limitations on Ethernet had to do with being able to detect collisions, the length of the packets, the speed of light, velocity factor, and like that; if you made the network too long, you couldn't detect collisions, and all was chaos.
Since we went to switches, that's not an issue, and simultaneously, Ethernet PHYs got *much* more impressive; you can go half a mile on copper now, as long as you don't get too close to fluorescent lights.
A similar thing has happened with RS-485 transceivers over time; the distance/noise issues have gotten better, as has the amount of load the receiver places on the line. Different transmitters can be at different ends of the specification tolerance, as well...
@Mike Donovan 100 Metres / ~330' comes to mind but DON'T QUOTE ME.
Err, 2&3..... using pins 1&2.
DMX over copper, theoretically 1640' with perfect equipment and circumstances. That doesn't mean 1641' won't work, however. Or that 1639' will always be trouble-free. Some say 1000'. It's really a moot point, as likely anything over 500' will have a different transport mechanism than raw DMX512 over copper or even fiber-optic.
My understanding is that this is related to the reality that in the time between when DMX became a standard and RDM became a standard, many cables were made with only three conductors given that pins 4 and 5 went unused. Rather than adding the additional headache of needing "rdm compatible cables" RDM was squeezed into the pins 2 and 3. It makes it grosser, but more likely to work.
100 metres/330' is the normal copper segment length for ethernet transmissions (cat5e, cat6, etc). DMX is nominally 1640', though I certainly wouldn't want to coil that cable...
Perhaps somewhere around about 1,640' per ETC's recommended maximum length of Ethernet? It's like they know...