Selecting the Right Switcher for the Job

Switchers are categorized by three primary considerations: size, format, and control options. Once you have determined the best size and format for your job, you should be able to make the product selection from the control optons.

Size

The size of a switcher is determined by the number of inputs it offers. A 6-In 1-Out switcher, for instance, offers up to six inputs and one output. It is common to select a switcher that offers more inputs than you actually need, especially if you feel that the system might require expansion at some point. If you cannot find a switcher that is large enough for your system, it is quite easy to expand the size by simply using additional units. For example, two 6-In 1-Out switchers can be used to create an 11-In 1-Out switcher. 

Format

Format refers to the primary function of a switcher. To clarify what this means, it is important to understand the differences between signal format, connector format, and resolution format, as these terms are often used interchangeably, causing confusion.

Signal Format

Signal format describes the manner in which the video and sync components of a signal are handled.Typical analog computer video signal formats contain high-bandwidth frequencies on the order of 30 MHz to 300 MHz, and include:

• RGBHV — Red, Green, Blue, Horizontal Sync, and Vertical Sync
• RGBS — Red, Green, Blue, and Composite Sync
• RGsB — Red, Green with composite sync, and Blue.
• Analog broadcast video signal formats include: composite video, S-video (Y/C), and component video (Y, R-Y, B-Y or Y, Pb, Pr), which have a bandwidth of 6 MHz for standard definition, or slightly less than 30 MHz for high definition (HDTV). In most cases, a switcher that is designed to pass computer video (RGB) format signals will also pass broadcast video signals through the Red, Green, and/or Blue channels. Switchers that utilize relays internally can typically also pass video through channels dedicated to passing sync.

Resolution Format

Resolution format describes the number of pixels and lines in a given video image. The term “VGA” technically refers to a specific resolution format of 640 x 480 (640 pixels horizontally by 480 lines vertically), typically at a refresh rate of 60 frames per second. More common resolution formats used by today's computers and display devices include XGA (1024 x 768 pixels) and SXGA (1280 x 1024), with other, higher resolution formats becoming increasingly more common. Switchers do not change a signal resolution format-they only pass it through. It is critical to insure that the display equipment used in a system is compatible with the source equipment in terms of signal resolution.

Connector Format

Connector format describes the physical interconnect type. The most common computer video interconnect is the 15-pin HD connector, used on most personal computers and on many ALTINEX switchers. This connector is often referred to as a “D-Sub connector,” “15-pin D-sub connector,” “15 pin DB connector,” or “VGA” connector, although is usually used to pass some type of VGA, SVGA, XGA, SXGA, or UXGA resolution format. 

This connector can be adapted for use on a variety of computers that do not use the 15-pin HD connector, such as Sun, SGI and older Apple Macintosh computers. See the “Cables” section of this catalog for information on converting connector formats.

In signal management systems, the BNC connector is also commonly used for both broadcast video and computer video because it provides a durable, high quality connection. Four BNC connectors must be used to pass RGBS and five BNC connectors must be used to pass RGBHV. A switcher described as handling “RGBHV” will also be able to pass RGBS and RGsB, as well as composite video, S-video, and component video, if the appropriate channels are used. Similarly, a VGA-QXGA switcher actually passes an RGBHV signal format on a 15-pin HD connector format.

Switcher Control/Auto Switching

In selecting a switcher for a system, it is also important to consider how the switcher will be controlled. Most ALTINEX switchers offer a built-in front panel control as well as RS-232 and/or contact closure remote control. 

Several models also offer the ability to provide auto switching, a feature which enables the selection of a source signal upon sensing an active input. This feature is ideal for creating user-friendly presentation systems with “automatic” functionality.

Common Features

Many of the features that are designed into our switchers apply to all of the available models. These features include:

• High bandwidth for passing high resolution signals without image degradation.
• Female connectors to increase reliability. A product with male connectors can be completely disabled by connector misalignment from a user.
• Detachable cables to increase flexibility and longevity. Hard-wired cables are easily damaged and difficult to replace. They also offer a fixed solution in terms of cable length.

Metal enclosures to insure durability. ALTINEX switcher enclosures are made from solid aluminum, providing an ideal combination of strength and light weight.

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