As the entertainment industry nears the 21st century, manufacturers of lighting control technology are faced with the unique challenge of utilizing technology that can be tailored to a wide variety of customers, while at the same time allowing for long-term growth and the seamless integration of multiple control systems. In an ideal world this technology would be scalable to suit any customer's needs, it would be affordable to suit anyone's budget, and it would be reliable to ensure everyone's peace of mind. In the real world this technology is called ethernet.
Ethernet was invented at the Xerox Palo Alto Research Center in the 1970s by Dr. Robert M. Metcalf. It was designed to support research on the "office of the future", providing a way for personal workstations to share data. One of the earlier examples of ethernet usage in theatrical lighting occurred with the introduction of the ethernet-compatible Obsession control console, unveiled at LDI92 in Dallas. The Obsession utilized ethernet to provide remote access to video displays and DMX512 outputs over a single cable. In the seven years since, nearly every lighting manufacturer has found a use for ethernet in their products, including in entry-level control consoles traditionally marketed to smaller facilities like churches and high schools. Today, ethernet technology can be found in Strand's ShowNet(TM) Electronics Diversified's Integrated Control Environment (ICE), and Colortran's ColorNet, among other applications.
The term ethernet refers specifically to a set of standards for connecting computers so that they can share information over a common wire or network. The IEEE 802.3 standard defines the electrical specifications for the types of wire and connectors that link computers together. There are other standards to define formats by which data is transmitted over the wire (TCP/IP, for example) that are also grouped under the "ethernet" umbrella.
Ethernet has several advantages over other existing communication standards. It is the established standard for networking business computers, so many qualified sources for installation, equipment and maintenance already exist. Ethernet is also a high-bandwidth communication medium. This means that a single network can carry all the data commonly required by an entertainment control system at extremely high rates of speed. Finally, an ethernet-based control system is bi-directional, which means that devices on the network can both receive instructions and report the status of the devices on the network to a central location.
Over the past several years, the cost of ethernet has dropped considerably, benefiting from the economies of scale provided by its use in the computer industry. This cost reduction can be seen in everything from cables to hubs to the ethernet card in a lighting designer's laptop computer. The availability of common ethernet hardware is another inherent advantage. Have you ever tried to find a five-pin XLR connector or DMX512 opto-splitter in Las Cruces, NM, on a Saturday? You can't. But you can buy ethernet cables and hubs at almost any computer store.
With the relative low cost and ready availability of ethernet components, entertainment lighting manufacturers and other industries have embraced ethernet with great gusto. Today ethernet is used in everything from high-end computing to amusement-park turnstiles.
A simple network configuration would consist of a number of devices (nodes) linked together by a common wire. An ethernet node is a device that can receive instructions over the network and then, based on those instructions, perform the function it is designed for. A DMX node, for example, is basically a translation box that can receive commands from a control console on an ethernet wire, translate that information into DMX512 levels, then transmit DMX512 information over another wire to a dimmer rack.
Nodes can be linked together using different cabling schemes that are determined by the type of cable used. For example, a thinnet (10base2) network connects nodes using a bus topology. This means that devices are connected in series by a single continuous cable. Each node is connected by a T connector tapped directly into the thinnet cable, and no "star" configuration is allowed. Unfortunately, thinnet cannot accommodate the higher bandwidth requirements currently called for in many markets, so its usefulness in the future is limited. The bus topology commonly used in thinnet networks is also something to consider, since a cable failure (remember, there's only one cable) will disrupt activity on the entire network.
A more fault-resistant network can be accomplished by using unshielded twisted-pair (10baseT, also referred to as UTP) cabling, connectors, and hubs. UTP cable is an eight-conductor cable that allows for a star configuration by using a network hub to connect the nodes. The network hub (sometimes called a concentrator) serves many functions. One function is to provide a central location with discrete inputs for all cables in the network to connect to. This makes UTP networks very robust, since a single cable failure will not compromise the entire network. Another function is to swap the send and receive pairs of the UTP cables to allow bi-directional communication. This pair swapping is a requirement of UTP cable conventions.
An ethernet system using UTP cable has a maximum length of 100m (328') between network devices. However, since another function of a network hub can be to act as a repeater, it's possible to double the effective network length to 200m (656'). In larger installations where very long runs are required, UTP wiring can be used in conjunction with a fiber-optic backbone to create a network that's both easy to troubleshoot and capable of covering up to 2,000m (6,560'). And for even larger networks it's possible to use a combination of multiple hubs, fiber, and UTP.
Most UTP networks currently transfer 10Mbps (megabits per second) of data; that's 40 times the bandwidth of DMX512. More importantly, UTP cabling supports 100Mbps (fast ethernet), which is currently supplanting the old 10Mbps standard. Gigabit ethernet, which is not yet in common use, will send 100 megabytes of data per second. That's fast enough to back up a standard computer hard drive in under a minute. Currently, all but the most elaborate entertainment systems easily get by using 10baseT.
Devices on a network talk to each other by sending information in "packets". A packet can be sent and/or received from any device (node) on the network. Simply speaking, a packet might contain a single data type, like DMX512 or console video, with an address tag on the front end that identifies the type of information the packet contains. Ethernet nodes monitor the data packets as they go by on the network, but only accept those specifically addressed to them. That's how ethernet networks serve different types of devices with the same cable. And since each packet goes to every device on the network (in a simple network configuration), a single message can carry information to more than one device. In more advanced networks, a network switch can be used to divide the network into smaller subnets. A switch increases the volume of information the network can handle because it helps manage the flow of data across the various subnets.
Before ethernet, most lighting system access was "hard-wired" through the control console. This forced designers and technicians to wait in line to complete their work, and posed difficult challenges when it came time to reconfigure a system for a special application. If the designer was entering cues, the control system was tied up until cueing was finished. This meant that the electricians had to wait for the designer to finish before they could begin work on their notes, adding to production time. A networked system facilitates multi-tasking on a level previously unheard of. In an industry besieged by deadlines, the ability to have many people using different parts of the control system simultaneously is fast becoming a requirement of any large-scale production.
The adoption of the DMX512 control standard answered the call for better interconnectivity, but recently the limitations of DMX512-based systems have become apparent in installations that require large amounts of distributed data. Running distributed data throughout a facility has traditionally meant pulling many different types of cable for each desired function - this is both expensive, and for most practical purposes, difficult to change once the installation is complete. Ethernet allows for a more flexible installation since it's both easy to add devices to a network and possible to reconfigure them for different functions once they have been installed.
With ethernet, gone are the days of running a half dozen drop cables for three ports of DMX out, DMX in, remote focus and dimmer feedback. In a networked environment a single cable can handle all of this data, including dimmer levels to the racks. It quickly becomes clear that the ability to remotely configure such devices to do multiple tasks would also be beneficial. On a networked system all of the devices are already physically connected via ethernet, so it's a small leap to be able to change the function of a remote port on a node. Want that DMX512 output to take DMX512 in? No problem: just log onto the network and change it.
Unlike control consoles, few dimmer racks, moving lights, or other devices currently provide direct ethernet support. However, these devices can easily be addressed on a network by using various types of interface equipment (ethernet nodes). Most lighting manufacturers offer a number of different interfaces to bridge the technology gap, each with a different selection of data outputs to talk to the dimmer racks. These interfaces can be permanently installed or portable. The most flexible systems might include a combination of installed and portable nodes, which can be connected to the ethernet system as needed.
While lighting manufacturers have agreed to make their equipment compatible with the DMX512 communications standard, they have not yet agreed on a common ethernet protocol. Currently, while there are standards for the physical components of a network and for the addressing and formatting of different types of ethernet packets, there are no standards for the contents of the packet itself. Manufacturers in the entertainment lighting industry retain their own proprietary data standards, and as a result their gear is not compatible on the same network. The Entertainment Services and Technology Association (ESTA) is working with the lighting industry to create ethernet standards that will allow interoperability.
At present, many ethernet nodes are multifunctional, providing connections for several types of control or output. They may allow functionality to a secondary control center outside the main control booth or a simple video display at the tech table. Often, nodes are installed onstage, in the dimmer room, or in a technical office. Ethernet nodes can interface with remote devices such as remote focus units, DMX512-capable moving lights, and DMX512 dimmer racks. The distribution of these signals may go around the stage, up to the catwalk, or to other remote points as they are needed. As use of ethernet matures and becomes more affordable, lighting manufacturers are designing simpler nodes with more specific functions.
One of the more common ethernet nodes is a video interface that provides remote access to the main console's video displays. The most common application is to provide console video and cue data at a designer's position, focus table, or stage manager panel. And since an ethernet node can be placed anywhere on the ethernet network, other applications are limited only by the system designer's imagination.
A focus call can use a video node and a remote focus unit right on the stage, without tying up the main console. A stage manager can monitor a cuesheet display from the main console during a performance.
Ethernet lets you create an enhanced tech table by allowing a facility to use a remote console that connects to the main console or even a personal computer over the network. In addition to providing console video and I/O, remote consoles include all or most of the buttons, faders, wheels encoders, etc. on the main console. This allows for simultaneous programming. For example, if you have a mixture of conventional and automated fixtures, one programmer can use the main console for the conventional fixtures and a second programmer can cue the automated fixtures with the remote console. Ethernet transfers the keystrokes entered at the remote console to the main console so that playback from the main console incorporates those commands into a single event. This means only one console is needed for the performance.
Installing new ethernet nodes on an existing network is a relatively straightforward process, well within the capabilities of the average electrical contractor or stage electrician. The fact that ethernet allows for such flexibility encourages system designers and consultants to think about integrating multiple control systems on a common network.
The ability to integrate theatrical control systems with architectural systems is another attractive feature to both customers and manufacturers. An entertainment system integrated with a common ethernet protocol (TCP/IP, for example) means that it's possible to have many different types of backup systems on a network and even the ability to log in from a remote location and check the status of the system.
A multiple-use facility, such as a large convention center, puts ethernet to prime use, linking entertainment and architectural systems. Consider a facility where ethernet links five Obsession II lighting control consoles with a half-dozen different Unison CMEi architectural control processors. The CMEi's can all output levels to any of the 17 Sensor SR48AF dimmer racks installed onsite. Scattered around the facility are 20 different DMX512 and video nodes. All of these devices are linked to the network via a network switch and numerous fiber-optic network concentrators.
The specification for this convention center requires the ability to patch and control any dimmer in the system from any of the multiple control consoles or the architectural system. To address the sheer scale of this convention center, it would be prudent to create a network divided into subnets. This means utilizing available network hardware (hubs and switches) and encapsulating the data into a format that the hardware can recognize. TCP/IP (the same format people use to access the Internet) can be used to route information to various parts of the facility.
In this application, it's possible to have all of the theatrical consoles competing for the same dimmers as the architectural system. As you can imagine, this presents some unique problems not found in conventional DMX512-based systems. In conventional control systems, if there are two inputs to a single dimmer in a rack, the competing levels will simply pile on to one another. Now with the possibility for up to six different inputs, well, what's a dimmer to do?
By developing an ethernet protocol that allows for multiple control systems to arbitrate who has control of what dimmer, it's possible to make large integrated control systems easier to manage for the end user. When the user boots up an Obsession II console anywhere in the facility, the console will ask what dimmers the user would like to control. The user has the option to take control of any dimmer in the system, and in doing so, gain control of lobby lights or even the dimmers that might have been previously controlled by the Obsession II down the hall. This is especially useful when a moving partition is removed and you need to combine two separate control systems into one.
The Obsession II processor then sends a message to the rest of the control systems to let them know that it now has control of a specific group of dimmers. This information is also shared with the Unison architectural system, which, in the event of a console failure, can then take control of the failed console's dimmers and set them to a predetermined level.
A convention center represents just one possible scenario where ethernet can facilitate the move toward truly integrated lighting control systems. By using available ethernet technology, a centralized control system can be created to provide seamless transition from what were previously two discrete control systems.
To be sure, ethernet has its opponents. Because it is relatively new to the entertainment industry, stage technicians, for example, will have to learn about this new networking technology. However, they may not realize how much they already know about networking that can be applied to ethernet (wiring, terminating, bus architectures) and how many more (human) resources are available when they need help. A Category Five ethernet network is the same in an office or a theatre, and the same contractors can easily be called to service both.
Some people may believe current approved Category Five ethernet wiring is flimsy and prone to damage, particularly in touring situations. It's true that ethernet cables and connectors are lightweight--that's what makes them cheaper. But even though an ethernet cable may be a little easier to damage, it's a lot easier to replace. And with ethernet, a single set of replacement cables covers all the equipment in a show. Traditional control may require four or five sets of expensive cables, multiplying the chance for damage, and the costs of keeping replacements on hand. After all, current control cables aren't immune to damage either. A forklift can crush DMX512 and ethernet cable with equal efficiency.
As we noted earlier, different companies use different data standards for their ethernet devices. For example, you can't connect an ETC console directly to a Strand dimmer rack with ethernet, even though both devices understand DMX512. However, adding a DMX node at one end or the other would make a connection possible, and ESTA is currently working on a uniform ethernet protocol to increase interoperability between products from different companies. That's how DMX became a theatrical standard, and ethernet will follow it in a few years.
In addition, some people make the wrong assumption that networking will be expensive. Generally speaking, ethernet wiring is cheaper than most other theatrical control cabling, and one ethernet cable can replace 4 or 5 other types of control networks. Today, theatrical networks do require converters to get many devices to use ethernet data, but converters are becoming more common and less expensive, and more and more devices are becoming ethernet capable. Even though small installations are still cheaper to install using traditional control, ethernet is becoming more and more economical as time passes. At some point in the not-too-distant future, ethernet could become the best answer for every application.