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Black Box Explains... Digital Visual Interface (DVI).

The Digital Visual Interface (DVI) video standard is based on transition-minimized differential signaling (TMDS). In a typical single-line digital signal, voltage is raised to a high level and decreased to... more/see it nowa low level to create transitions that convey data. To minimize the number of tran-sitions needed to transfer data, TMDS uses a pair of signal wires. When one wire goes to a high-voltage state, the other goes to a low-voltage state. This balance increases the data-transfer rate and improves accuracy.

Although there are four types of DVI connectors, only DVI-D and DVI-I are commonly used for monitors. DVI-D is a digital-only connector. DVI-I supports both digital and analog RGB connections. collapse


Black Box Explains…TEMPEST.

TEMPEST is an acronym for Telecommunications Electronics Material Protected from Emanating Spurious Transmissions. It pertains to technical security countermeasures, standards, and instrumentation that prevent or minimize the exploitation of vulnerable... more/see it nowdata communication equipment by technical surveillance or eavesdropping.

What puts your data communication equipment at risk? Many things. But first and foremost, its microchip.

Any device with a microchip generates an electromagnetic field, often called a “compromising emanation” by security experts. With the proper surveillance equipment, these emanations can be intercepted and the signal reconstructed and analyzed. Unprotected equipment can, in fact, emit a signal into the air like a radio station—and nobody wants to risk his or her job and a whole lot more by broadcasting national security or trade secrets to the wrong people.

Some of the most vulnerable devices are speakerphones, printers, fax machines, scanners, external disc drives, and other high-speed, high-bandwidth peripherals. If the snoop is using a high-quality interception device, your equipment’s signals can be acquired up to several hundred feet away.

Arguably one of the most vulnerable pieces of equipment is an analog VGA monitor. If a spy were to introduce a Trojan into your system, he or she could monitor and store key presses and passwords used during the day. When the system’s not in use at night, the spy could pulse the VGA screen with grayscale images that have a strong signal at particular frequencies. VGA uses single-ended signaling that has a high common-mode emission level not protected by cable shielding, and it’s possible to monitor these signals outside the secure zone using a radio receiver. Even without a Trojan, a sophisticated receiver located nearby picks up and views what’s on the VGA monitor.

What TEMPEST is and isn’t.
It should come as no surprise that the Federal government became concerned about signal leakage. In fact, its interest goes back to the days of World War I when the Army was trying to exploit weaknesses of enemy combat phones and radio transmitters. Since then, the scope of the government’s interests has broadened beyond battlefield equipment. In the last 40 years, the National Security Agency (NSA) has taken several industry measurement standards and greatly beefed them up. These enhanced criteria are commonly referred to as the TEMPEST standards (although the NSA also calls them EMSEC standards, short for “emissions security”).

TEMPEST disciplines involve designing circuits to minimize emanations and the application of appropriate shielding, grounding, and bonding. Some methods used include radiation screening, alarms, and isolation.

A TEMPEST-approved device resembles its non-secure version with a few key differences. If it’s a network component such as a switch, it comes in a heavy metal case. It also has special shielding, a modified power supply, and perhaps a few other modifications from the standard model. If you need to open the device’s case, a special torque wrench for use with TEMPEST-only products is required.

TEMPEST test equipment is very expensive and is sold exclusively to government agencies. Nobody can sell you commercial TEMPEST testing equipment. And if someone offers you a “TEMPEST surveillance system,” you need to be aware of two things: First, TEMPEST is counter-surveillance science and the offer is a fraud; second, the salesperson is committing a federal felony.

If you buy surveillance equipment—authentic or not—then you have also commited a felony. Construction of, possession of, attempting a sale of, or attempting a purchase of said surveillance equipment is illegal. Even if the product purchased is a hoax, the law will take your intentions into account as much as the salesperson’s. Don’t be surprised if you both go to jail.

In the United States, you can learn about TEMPEST testing only in special schools sanctioned by, if not run by, the NSA. Courses to earn the TEMPEST Technician or TEMPEST Engineer certifications are very expensive. These classes are offered to a limited number of people who have a very high level of security clearance and who will be working on TEMPEST-approved equipment all the time.

TEMPEST ratings.
All TEMPEST-approved communication devices have a rating based on their application and/or environment.

Type 1: This rating is for classified cryptographic equipment used for national security purposes. It’s endorsed by the NSA for securing telecommunications and automated information systems and for the protection of classified or sensitive U.S. Government information.

Type 2: This rating is for unclassified cryptographic equipment used by U.S. Government agencies, state and local governments, and sponsored U.S. Government contractors. It’s endorsed by the NSA for securing telecommunications and automated information systems and for the protection of unclassified but sensitive information, such as contract bids.

Type 3: This rating is for unclassified commercial cryptographic equipment that implements an algorithm registered with the National Institute of Standards and Technology (NIST). It’s for use in protecting sensitive information, like a corporation’s network communications. collapse


Black Box Explains... Matrix video switches.

Matrix switches enable computers to mix and match the output of multiple PCs on multiple video monitors.

For instance, if your operation has four PCs and you want to display the... more/see it nowvideo on one monitor to the other three monitors, a matrix video switch is what you need to handle the job. Use matrix switches for:
• Trade shows—Set up a wall of video to wow the senses of attendees.
• Transportation schedules—Provide real-time updates of flights or deliveries on multiple screens.
• Training demonstrations—Control each screen’s video to focus everyone’s attention on what’s important. collapse


Black Box Explains...Upgrading from VGA to DVI video.

Many new PCs no longer have traditional Cathode Ray Tube (CRT) computer monitors with a VGA interface. The latest high-end computers have Digital Flat Panels (DFPs) with a Digital Visual... more/see it nowInterface (DVI). Although most computers still have traditional monitors, the newer DFPs are coming on strong because flat-panel displays are not only slimmer and more attractive on the desktop, but they’re also capable of providing a much sharper, clearer image than a traditional CRT monitor.

The VGA interface was developed to support traditional CRT monitors. The DVI interface, on the other hand, is designed specifically for digital displays and supports the high resolution, the sharper image detail, and the brighter and truer colors achieved with DFPs.

Most flat-panel displays can be connected to a VGA interface, even though using this interface results in inferior video quality. VGA simply can’t support the image quality offered by a high-end digital monitor. Sadly, because a VGA connection is possible, many computer users connect their DFPs to VGA and never experience the stunning clarity their flat-panel monitors can provide.

It’s important to remember that for your new DFP display to work at its best, it must be connected to a DVI video interface. You should upgrade the video card in your PC when you buy your new video monitor. Your KVM switches should also support DVI if you plan to use them with DFPs. collapse


Black Box Explains...UTP cable and color drift.

UTP cable is often used with video or KVM extenders to extend the reach of a video signal. It’s popular for this application because it’s lightweight, easy to handle, and... more/see it nowinexpensive. But when you transmit video over long stretches of twisted-pair cable, you sometimes run into a phenomenon called color drift or color split.

Color drift shows up as that annoying colored shadow you occasionally see around objects on a video screen. It sometimes happens with UTP cable because the pairs of wire in the cable are twisted at slightly different rates to reduce crosstalk between pairs. Because of these differences between wire pairs, video signals for different colors often travel different distances before they reach the remote receiver. When one color signal arrives behind the others because its wire is longer, you get that red, green, or blue shadow around the objects on your video screen.

UTP cable varies widely by manufacturer, so before installing video extenders, it’s difficult to determine whether or not you’re going to have a color drift problem. You’re more likely to experience color drift with higher grades (CAT5e or CAT6) of cable, on longer cable runs, and on high-resolution screens.

If you experience color drift, there are several possible solutions. You can use a shorter length of cable, switch from CAT5e or CAT6 cable to CAT5 cable, use a lower screen resolution, or use a video skew compensator.

A video skew compensator removes color drift by delaying some color signals to compensate for differences in wire pairs. collapse


Black Box Explains...Types of KVM switches.

Black Box has the keyboard/video switches you need to share one CPU between several workstations or to control several CPUs from one monitor and keyboard.

If you do a lot of... more/see it nowswitching, you need premium switches—our top-of-the-line ServSwitch™ KVM switches give you the most reliable connections for the amount of KVM equipment supported. With ServSwitch KVM switches, you can manage as many CPUs as you want from just one workstation, and you can access any server in any computer room from any workstation. Eliminating needless equipment not only saves you money, it also gives you more space and less clutter. Plus, you can switch between PCs, Sun®, and Mac® CPUs. ServSwitch KVM switches can also cut your electricity and cooling costs because by sharing monitors, you use less power and generate less heat.

If your switching demands are very minor, you may not need products as advanced as ServSwitch. Black Box offers switches to fill less demanding needs. Most of these are manual switches or basic electronic switches, which don’t have the sophisticated emulation technology used by the ServSwitch.

For PCs with PS/2® keyboards, try our Keyboard/Video Switches. They send keyboard signals, so your CPUs boot up as though they each have their own keyboard.

With the RS/6000™ KVM Switch, you can run up to six RS/6000 servers from one workstation. Our Keyboard/ Video Switch for Mac enables you to control up to two Mac CPUs from one keyboard and monitor.

With BLACK BOX® KVM Switches, you can share a workstation with two or four CPUs. They’re available in IBM® PC and Sun Workstation® configurations.

You’ll also find that our long-life manual Keyboard/Video Switches are perfect for basic switching applications. collapse


Black Box Explains... ServSwitch Multi and audio cable.

Get more out of your ServSwitch Multi. Add audio cable, a set of speakers, and a microphone to each CPU. Audio cable turns your ServSwitch Multi into the ideal system... more/see it nowfor education, training, retail, medical, and multimedia office environments.

Audio cable isn’t just for the ServSwitch Multi either. You can also use it with servers that give off audible alarms.

So even if you don’t have audio equipment now—plan ahead. When you’re ready to add audio equipment, just plug in our audio cable. collapse


Black Box Explains...USB 2.0 and USB OTG.

The Universal Serial Bus (USB) hardware (plug-and-play) standard makes connecting peripherals to your computer easy.

USB 1.1, introduced in 1995, is the original USB standard. It has two data rates:... more/see it now12 Mbps for devices such as disk drives that need high-speed throughput and 1.5 Mbps for devices such as joysticks that need much lower bandwidth.

In 2002, a newer specification, USB 2.0, or Hi-Speed USB 2.0, gained wide acceptance in the industry. This version is both forward- and backward-compatible with USB 1.1. It increases the speed of the peripheral to PC connection from 12 Mbps to 480 Mbps, or 40 times faster than USB 1.1!

This increase in bandwidth enhances the use of external peripherals that require high throughput, such as CD/DVD burners, scanners, digital cameras, video equipment, and more. USB 2.0 supports demanding applications, such as Web publishing, in which multiple high-speed devices run simultaneously. USB 2.0 also supports Windows® XP through a Windows update.

An even newer USB standard, USB On-The-Go (OTG), is also in development. USB OTG enables devices other than a PC to act as a host. It enables portable equipment—such as PDAs, cell phones, digital cameras, and digital music players—to connect to each other without the need for a PC host.

USB 2.0 specifies three types of connectors: the A connector, the B connector, and the Mini B connector. A fourth type of connector, the Mini A (used for smaller peripherals such as mobile phones), was developed as part of the USB OTG specification. collapse


Black Box Explains...Digital Visual Interface (DVI) and other digital display interfaces.

There are three main types of digital video interfaces: P&D, DFP, and DVI. P&D (Plug & Display, also known as EVC), the earliest of these technologies, supports both digital and... more/see it nowanalog RGB connections and is now used primarily on projectors. DFP (Digital Flat-Panel Port) was the first digital-only connector on displays and graphics cards; it’s being phased out.

There are different types of DVI connectors: DVI-D, DVI-I, DVI-A, DFP, and EVC.

DVI-D is a digital-only connector. DVI-I supports both digital and analog RGB connections. Some manufacturers are offering the DVI-I connector type on their products instead of separate analog and digital connectors. DVI-A is used to carry an analog DVI signal to a VGA device, such as a display. DFP, like DVI-D, was an early digital-only connector used on some displays; it’s being phased out. EVC (also known as P&D) is similar to DVI-I only it’s slightly larger in size. It also handles digital and analog connections, and it’s used primarily on projectors.

All these standards are based on transition-minimized differential signaling (TMDS). In a typical single-line digital signal, voltage is raised to a high level and decreased to a low level to create transitions that convey data. TMDS uses a pair of signal wires to minimize the number of transitions needed to transfer data. When one wire goes to a high-voltage state, the other goes to a low-voltage state. This balance increases the data-transfer rate and improves accuracy. collapse


Black Box Explains...Stream mode vs. burst mode/prompt mode.

Computers and mice must communicate with each other in order to operate properly. Most computers and mice communicate via a method called “stream mode”—as a mouse is being moved, it... more/see it nowsends the coordinates of its new position in a constant stream of information.

However, some computers communicate via a method known as “burst” or “prompt” mode. With this method, the mouse holds its data until the CPU sends a request (or “prompt”) for it. This mode of communication presents a problem for many KVM switches, as they normally pass along mouse coordinates in a stream mode. This results in a CPU receiving data when it isn’t expecting it, and the mouse simply won’t function properly.

All ServSwitch™ products contain support for stream-mode CPUs, and several ServSwitch products support both stream and burst/prompt modes. Call our FREE Tech Support about requirements for your application. collapse

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