Analog Video Matrix Switchers

The analog video matrix switcher, as we have noted, is the big brother of the sequential switcher. The bigger CCTV systems can only be designed with a video matrix switcher (VMS) as the brain of the system.

The name "matrix switcher" comes from the fact that the number of video inputs plotted against the number of video outputs makes a matrix, as it is known in mathematics. Quite often, video matrix switchers are called video cross- point switchers. These cross-points are actually electronic switches that select any video input onto any video output at any one time, preserving the video impedance matching. Thus, one video signal can simultaneously be selected on more than one output. Also, more video inputs can be selected on one output; only in this case we would have a sequential switching between more inputs, since it is not possible to have more than one video signal on one output at any single point in time.

Video matrix switchers are, in essence, big sequential switchers with a number of advancements:

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A matrix switcher can have more than one operator. Remember that the sequential switchers usually have buttons at the front of the unit. Thus, only one operator can effectively control the system at any one time. Matrix switchers can have up to a dozen operators, sometimes even more, all of whom can concurrently control the system. In such a case, every operator controls (usually) one video output channel. A certain intelligent control can be achieved, depending on the matrix in use. Different operators may have equal or different priorities, depending on their position in the security structure of the system.

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The matrix switcher accepts many more video inputs and accommodates for more outputs, as already mentioned, and more importantly, these numbers can easily be expanded at a later date by just adding modules.

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The matrix has pan, tilt, and lens digital controllers (usually referred to as PTZ controllers). The keyboard usually has an integral joystick, or buttons, as control inputs and at the camera end, there is a so-called PTZ site driver within a box that is actually part of the matrix. The PTZ site driver talks and listens to the matrix in digital language and drives the pan/tilt head together with the zoom lens and perhaps some other auxiliary device (such as wash/wipe assembly).

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The matrix generates camera identification, time and date, operator(s) using the system, alarm messages, and similar on screen information, superimposed on the video signal.

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The matrix has plenty of alarm inputs and outputs and can be expanded to virtually any number required. Usually, any combination of alarms, such as N/O, N/C, and logical combinations of them (OR, NOR, AND, NAND), is possible.

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In order for the matrix switchers to perform the very complex task of managing the video and alarm signals, a microprocessor is used as the brain. With the ever-increasing demand for power and processing capacity, microprocessors are becoming cheaper and yet more powerful. These days, full-blown PCs perform these complex processes. As a consequence, a matrix setup becomes programming in itself, complex but with immense power and flexibility, offering password protection for high security, data logging, system testing, and re-configuring via modem or network. The latest trend is in the form of the graphical user interface (GUI), using popular operating systems, with touch-sensitive screens, graphical site layout representation that can be changed as the site changes, and much more.

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The matrix might be very complex for the system designer or commissioner, but they are very simple and user friendly for the operator and, more importantly, faster in emergency response.

There used to be a handful of manufacturers of matrix in the world, not many of which are left today. Many of them have stayed with the traditional concept of cross-point switching and a little bit of programmability, usually stored in a battery-backed EPROM. Earlier concepts with battery-backed EPROMs, without recharging, could only last a few weeks. But many have accepted clever and flexible programming, with the system configuration stored on floppy disks or hard drives, preventing loss of data even if the system is without power for more than a couple of months. The demand for compatibility has forced many systems to become PC-based, making the operation familiar to the majority of users and at the same time, offering compatibility with many other programs and operating systems that may work in conjunction.

The new designs of matrix switchers take almost every practical detail into account. First of all, configuring a new system, or even re-configuring an old one, is as easy as entering details through a setup menu. This is, however, protected with high levels of security, which allows only authorized people who know the appropriate access code and procedures to play around with the setup.