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... Using fiber optics for KVM extension.
If you‘re sending KVM signals between buildings for an extended distance, in areas supplied by different power sources, in an electrically noisy environment, or where data security is a big... more/see it nowconcern, you need to use a fiber optic-based KVM extender.
Optical fiber is an ideal transmission medium not only for backbone and horizontal connection, but also for workstation-to-backracked CPU or server links. It works very well in applications where you need to transfer large, bandwidth-consuming data files over long distances, and where you require immunity from electrical interference or data theft.
The choice for extraordinary reach.
Fiber doesn’t have the 100-meter (328-ft.) distance limitation that UTP copper without a booster does. Fiber distances can range from 300 meters (984.2 ft.) to 70 kilometers (24.8 mi.), depending on the cable, wavelength, and network. With fiber-based KVM extenders, the transmitter converts conventional data signals into a modulated light beam, then transports the beam via the fiber to a receiver, which converts the light back into electrical signals.
Many newer fiber-based KVM extenders support both analog and digital transmission. Often, they work by digitizing video output from a local CPU, then sending it across fiber link to a remote unit, which converts it back to the original analog signal. In many cases, one fiber of the fiber pair transmits monitor video serially and the second fiber sends remote mouse and keyboard information back to the local CPU.
The choice for ensuring signal integrity.
Because fiber is made of glass, which is an insulator, no electric current can flow through. It’s immune to electromagnetic interference and radio-frequency interference (EMI/RFI), crosstalk, impedance problems, and more. This is why fiber-based KVM extenders are beneficial to users in process control, engineering, utility, and factory automation applications. The users need to keep critical information safe and secure off the factory floor but be able to access that data from workstations and control consoles within the harsh environments. Plus, fiber is also less susceptible to temperature fluctuations than copper is, and it can be submerged ?in water.
The choice for greater signal fidelity.
Fiber-based KVM extenders can carry more information with greater fidelity than copper-based ones can. For this reason, they’re ideal for high-data-rate systems in which multimedia workstations are used.
Newer KVM extenders enable you to send both DVI and keyboard and mouse signals over the same fiber cable, transmitting video digitally for zero signal loss. This way, you can get HD-quality resolution even at very long distances from the source. Users in university or government R&D, broadcasting, healthcare—basically anyone who depends on detailed image rendering—can benefit from this technology.
The choice for data security.
Plus, your data is safe when using fiber to connect a workstation with a CPU or server under lock and key. It doesn’t radiate signals and is extremely difficult to tap. If the cable is tapped, it’s very easy to monitor because the cable leaks light, causing the entire system to fail. If an attempt is made to break the physical security of your fiber system, you’ll know it.
Many IT managers in military, government, finance, and healthcare choose fiber-based KVM extenders for this very reason. Plus corporations, aware of rising data privacy concerns over customer billing information and the need to protect intellectual property, use this type of extension technology in their offices, too.
Considerations for fiber-based KVM extension.
Before selecting a fiber-based KVM extender, it’s important to know the limitations of your system. You need to know where couplers, links, interconnect equipment, and other devices are going to be placed. If it’s a longer run, you have to determine whether multimode or single-mode fiber cable is needed.
The most important consideration in planning cabling for fiber-based KVM extension is the power budget specification of device connection. The receiver at the remote end has to receive the light signal at a certain level. This value, called the loss budget, tells you the amount of loss in decibels (dB) that can be present in the link between the two devices before the units fail to perform properly.
Specifically, this value takes the fiber type (multimode or single-mode) and wavelength you intend to use—and the amount of expected in-line attenuation—into consideration. This is the decrease of signal strength as it travels through the fiber cable. In the budget loss calculation, you also have to account for splices, patch panels, and connectors, where additional dBs may lost in the entire end-to-end fiber extension. If the measured loss is less than the number calculated by your loss budget, your installation is good.
Testers are available to determine if the fiber cabling supports your intended application. You can measure how much light is going to the other end of the cable. Generally, these testers give you the results in dB lost, which you then compare to the loss budget to determine your link loss margin.
Also, in some instances, particularly when using single-mode fiber to drive the signal farther, the signal may be too strong between connected devices. This causes the light signal to reflect back down the fiber cable, which can corrupt data, result in a faulty transmission, and even damage equipment. To prevent this, use fiber attenuators. They’re used with ?single-mode fiber optic devices and cable to filter the strength of the fiber optic signal from the transmitter’s LED output so it doesn’t overwhelm the receiver. Depending on the type of attenuator attached to the devices at each end of the link, you can diminish the strength of the light signal a variable amount by a certain number of decibels.
Need help calculating your budget loss? Call our FREE Tech Support. If necessary, they can even recommend a fusion splicing fiber kit, a fiber tester, or a signal attenuator for your specific requirements.
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 cant 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...Digital Visual Interface (DVI) connectors.
DVI (Digital Video Interface) is the standard digital interface for transmitting uncompressed high-definition, 1080p video between PCs and monitors and other computer equipment. Because DVI accommodates both analog and digital... more/see it nowinterfaces with a single connector, it is also compatible with the VGA interface. DVI differs from HDMI in that HDMI is more commonly found on HDTVs and consumer electronics.
The DVI standard is based on transition-minimized differential signaling (TMDS). There are two DVI formats: Single-Link and Dual-Link. Single-link cables use one TMDS-165 MHz transmitter and dual-link cables use two. The dual-link cables double the power of the transmission. A single-link cable can transmit a resolution ?of 1920 x 1200 vs. 2560 x 1600 for a dual-link cable.
There are several types of connectors: DVI-D, DVI-I, DVI-A, DFP, and EVC.
DVI-D (digital). This digital-only interface provides a high-quality image and fast transfer rates between a digital video source and monitors. It eliminates analog conversion and improves the display. It can be used when one or both connections are DVI-D.
DVI-I (integrated). This interface supports both digital and analog RGB connections. It can transmit either a digital-to-digital signal or an analog-to-analog signal. It can be used with adapters to enable connectivity to a VGA or DVI-I display or digital connectivity to a DVI-D display. If both connectors are DVI-I, you can use any DVI cable, but DVI-I is recommended.
DVI-A (analog) This interface is used to carry a DVI signal from a computer to an analog VGA device, such as a display. If one connection is DVI and the other is VGA HD15, you need a cable or adapter with both connectors.
DFP (Digital Flat Panel) was an early digital-only connector used on some displays.
EVC (also known as P&D, for Plug & Display), another older connector, handles digital and analog connections.
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