PROTOCOLS - AN HISTORICAL PERSPECTIVE

The following article appeared in ESTA's Protocol, Spring 2000 issue, and is reprinted with permission.
© 2000 Entertainment Services & Technology Association.

 

By now just about everyone in the entertainment lighting industry has read or heard some retrospective on the amazing technological advancements that took place in the century just past. Think about it - the incandescent lamp was still in its infancy just 100 years ago, and to control its intensity you needed vats of salt water! Now here we are with computerized electronic dimmers, and we control robotic lights over high speed data communications networks. If you check out the March 2000 issue of Entertainment Design you'll see what a number of industry professionals have to say about what was accomplished in the 1900s.

 

There's a wide range of very thought-provoking opinion on what were the most significant advances, but to me it seemed -- not surprisingly - that most people pointed to inventions that had to do with improved control of show elements. And it was the adoption of standardized ways of accomplishing this control that many saw as critically important. Some advances that became standards, de facto or otherwise, include the ellipsoidal reflector spotlight (arguably more about controlling light than just producing it), the silicon controlled rectifier (SCR) dimmer, and asynchronous serial digital data communications (i.e. DMX512). The developments described here are part one of two related articles examining the evolution of lighting control protocols, how various manufacturers have implemented them, and moves toward standardization. Part two will offer technical information of interest to anyone with legacy dimming equipment that doesn't "speak" a standard language.

 

In the Old Days
When I started working for Electro Controls in the early 1970s, we were still producing a lot of autotransformer dimming systems, but by then the state of the art had become low voltage analog control of SCR dimmers. When this technique was pioneered in the '60s, it was regarded as a great leap forward since now it was possible to remotely control dimmers with a relatively small console that in some cases was even portable! Our company used a 0-15 volt DC signal to control each dimmer, but I soon discovered that other manufacturers had different ideas about what was the best way to do the job: Kliegl Bros., for example, used 0-28VDC, and Ward Leonard (anyone remember that name?) ran their systems on 24VDC. Strand seemed to be in favor of 0-10 volt control, but products made in Europe required 0 to minus 10 volts (many of these ended up in North America). These were by no means the only control methods around - EDI's 2-7.6VDC springs to mind. At EC most of our dimmers ran on DC control _no_tDC swor dy"pan> < terta" typ by A ranut I soon discovered that other manufacturers had different ideas about what was the best way tov id="jods . t: Jnpas t ndex.pa

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