Technology Showcase: Matrix Switchers
Sep 1, 2009 2:14 PM, By Jay Ankeney
Scalability is just one feature in a long list.
In the world of switchers, you need to know whose turf you are on if you want to understand the lingo. In the video production arena, a switcher is used to manipulate the audio/video material to create effects. In the IT world, a switch is the traffic cop for IP signals. In the pro AV game, however, the main goal of a switcher is to provide multiple pathways for multiple signals while getting them from input A to output B as pristinely as possible.
For many people in the pro AV world, the terms switcher, switch, and router are fairly interchangeable. For others, routers are considered intersections while switches are analagous to streets. Perhaps Dr. Samuel Johnson provided the most eloquent definition for this kind of networking device as, “any thing reticulated or decussated, at equal distances, with interstices between the intersections,” but then that was for his 1755 Dictionary of the English Language.
Modern routers or switchers were originally intended to replace hand-plugged patch panels to move signals around, as seen in classic film scenes of women at early switchboards jamming 1/4in. jacks into walls of holes while intoning, “Number pleeaze.” Crosspoint switchers have been around since the ’70s, with some of the first being developed by Grass Valley, Richmond Hill Labs, and TeleMation for use in television stations.
Today, there are routers or switchers designed to handle the whole spectrum of signals that pro AV deals with. These can include IP signals; multiple flavors of analog/digital computer, home theater, or production video and audio; and recently, “3 Gig” (3Gbps) bandwidth for 1080p images and even keyboard, video monitor, mouse (KVM) control protocols. One of the most elaborate classes of these “interstices between intersections” systems has grown to become the matrix switcher that, as the name implies, allows a bunch of incoming signals to get to any number of selected output destinations intact.
Conventionally, matrix switchers are described by the number of inputs against the number of outputs, expressed for example as 32x32. In fact, anything from 8x8 to 32x32 is considered among the smaller class of matrix switchers. It can extend up to the thousands for larger matrix switchers, and with some newer modular designs, the upper limit is left to the imagination of the system installer.
Maintaining the required signal integrity involves more than just spreading the flow to multiple ports. A digital matrix switcher needs to have a receiving buffer circuit on its input that regenerates the signal to its nominal level. The digital signal is then passed unprocessed through a crosspoint matrix made up of large-scale integrated circuits that direct it to the desired output. Once it’s there, a digital video driver chip is evoked to re-establish its level to 800mV while a reclocking circuit puts the signal into a more stable time base before it is distributed to its destination device.
The inputs of an analog matrix switcher have some kind of equalization circuitry, usually compensating for the high-frequency roll-off accrued during cable delivery. After steering it through the crosspoint array composed of discrete components, an output driver restores the signal to the nominal level of 1V peak-to-peak, matches its impedance, and presents it to the desired destination.
The traditional design philosophy of matrix switchers has been to make them as transparent as possible, but in recent years, some manufacturers have proposed the idea that adding format-conversion capabilities built into the system has enabled some of them to convert baseband signals from analog to digital or digital to analog and from one format to another. Others leave that to external devices.
Matrix switchers are increasingly being used in settings that involve destination systems of many heritages and each with their own legacy. Commonly used throughout corporate installations, digital signage networks, command and control centers, university campuses, sports complexes, and even simulation theaters, matrix switchers need to serve the needs of a variety of solicitors.
That is why reliable 24/7 operation is key, so most matrix switchers have redundant power supplies and several forms of internal diagnostics. They can also be manipulated by an equally wide assortment of controllers, either external IP web interfaces, RS-232 devices, or onboard control panels. Control of the switcher can also be facilitated by routing KVM signals to keyboards throughout the system.
Recognizing that modern matrix switchers cover a wide spectrum of applications, each with a burgeoning array of features, here is a look at some of the most interesting offerings from the major manufacturers.
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