in Buyer's Guides
For a PDF of the Jan. 2009 PLSN Buyers Guide, CLICK HERE .
A decade ago, Ethernet was to our industry what ethics and morals were to politics — a great idea that’s not commonly used in practice. Politics hasn’t changed, but our industry has.
When DMX was introduced in 1985, it was never intended to run automated lights, much less media servers with hundreds of control channels and arrays of LEDs numbering in the tens of thousands. At the time, a baud rate of 250K, which is the speed of transmission of DMX, was just fine, and the 512 channel limit of a single universe of DMX was not an issue.
Then came the Britney Spears of the world, and the typical lighting rig morphed into the Godzilla rig with scores of automated lights, multiple media servers and more LED pixels than you can count with an abacus. Gradually, the channel count in a typical show outgrew the channel count of a single DMX universe until it reached proportions as large as 83 universes, as was the case in the Opening Ceremonies of the Games of the XXIX Olympiad in Beijing last summer.
It has become obvious that transmitting multiple universes of DMX over Ethernet has its advantages. A single Cat 5 cable running 10Mb Ethernet can transmit about 20 universes of DMX; 100Mb Ethernet can transmit about 200 universes of DMX; and Gigabit Ethernet can transmit about 2000 universes of DMX.
But Ethernet is not the be-all, end-all solution for data distribution. First, it can only be run about 300 feet before the signal degrades. Second, it is a star topology, meaning that each device has to have its own cable from the hub. Third, Ethernet connectors are more expensive than XLR connectors.
So today’s data distribution systems are typically a hybrid of Ethernet and DMX. Many consoles now output a protocol that is intended to be run over Ethernet, such as ArtNet, ETCNet, ShowNet, Pathport, or ACN. They can plug directly into a Cat 5 system using off-the-shelf Ethernet hubs, switches, bridges, and Wi-Fi. But most devices still require a DMX input. That’s where the products in this month’s Buyer’s Guide come in.
The number of DMX-to-Ethernet (and vice versa) products is growing in proportion to the growth of networking in general. Here’s a sample of some of the latest products that will help you build a state-of-the-art data distribution network.