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Black Box Explains...SCSI Ultra2 and LVD (Low-Voltage Differential).

Small Computer Systems Interface (SCSI), pronounced “scuzzy,” has been the dominant technology used to connect computers and high-speed peripherals since the 1980s. SCSI technology is constantly evolving to accommodate increased... more/see it nowbandwidth needs. One of the more recent developments is Ultra2 SCSI.

Because Ultra2 SCSI is backward compatible, it works with all legacy equipment. Ultra2 doubles the possible bandwidth on the bus from 40 to 80 MBps! Just as importantly, Ultra2 supports distances up to 12 meters (39.3 ft.) for a multiple-device configuration. Ultra2 uses Low-voltage Differential (LVD) techniques to transfer data at faster rates with fewer errors. Don’t confuse Ultra2 with LVD. Ultra2 is a data-transfer method; LVD is the signaling technique used to transfer the data.

Cables are very important when designing or upgrading a system to take advantage of Ultra2 SCSI. Cables and connectors must be of high quality and they should come from a reputable manufacturer to prevent crosstalk and minimize signal radiation. BLACK BOX® Ultra2 LVD cables are constructed of the finest-quality components to provide your system with the maximum protection and highest possible data-transfer rates. collapse


Black Box Explains...10-Gigabit Ethernet.

10-Gigabit Ethernet (10-GbE), ratified in June 2002, is a logical extension of previous Ethernet versions. 10-GbE was designed to make the transition from LANs to Wide Area Networks (WANs) and... more/see it nowMetropolitan Area Networks (MANs). It offers a cost-effective migration for high-performance and long-haul transmissions at up to 40 kilometers. Its most common application now is as a backbone for high-speed LANs, server farms, and campuses.

10-GbE supports existing Ethernet technologies. It uses the same layers (MAC, PHY, and PMD), and the same frame sizes and formats. But the IEEE 802.3ae spec defines two sets of physical interfaces: LAN (LAN PHY) and WAN (WAN PHY). The most notable difference between 10-GbE and previous Ethernets is that 10-GbE operates in full-duplex only and specifies fiber optic media.

At a glance—Gigabit vs. 10-Gigabit Ethernet

Gigabit
• CSMA/CD + full-duplex
• Leveraged Fibre Channel PMDs
• Reused 8B/10B coding
• Optical/copper media
• Support LAN to 5 km
• Carrier extension

10-Gigabit Ethernet
• Full-duplex only
• New optical PMDs
• New coding scheme 64B/66B
• Optical (developing copper)
• Support LAN to 40 km
• Throttle MAC speed for WAN
• Use SONET/SDH as Layer 1 transport

The alphabetical coding for 10-GbE is as follows:
S = 850 nm
L = 1310 nm
E = 1550 nm
X = 8B/10B signal encoding
R = 66B encoding
W = WIS interface (for use with SONET).

10-GbE
10GBASE-SR — Distance: 300 m; Wavelength: 850 nm; Cable: Multimode
10GBASE-SW — Distance: 300 m; Wavelength: 850 nm; Cable: Multimode
10GBASE-LR — Distance: 10 km; Wavelength: 1310 nm; Cable: Single-Mode
10GBASE-LW — Distance: 10 km; Wavelength: 1310 nm; Cable: Single-Mode
10GBASE-LX4 — Distance: Multimode 300 m, Single-Mode 10 km; Wavelength: Multimode 1310 nm, Single-Mode WWDM; Cable: Multimode or Single-Mode
10GBASE-ER — Distance: 40 km; Wavelength: 1550 nm; Cable: Single-Mode
10GBASE-EW — Distance: 40 km; Wavelength: 550 nm; Cable: Single-Mode
10GBASE-CX4* — Distance: 15 m; Wavelength: Cable: 4 x Twinax
10GBASE-T* — Distance: 25–100 m; Wavelength: Cable: Twisted Pair
* Proposed for copper. collapse


Black Box Explains...Loose-tube vs. tight-buffered fiber optic cable.

There are two styles of fiber optic cable construction: loose tube and tight buffered. Both contain some type of strengthening member, such as aramid yarn, stainless steel wire strands, or... more/see it noweven gel-filled sleeves. But each is designed for very different environments.

Loose tube cables, the older of the two cable types, are specifically designed for harsh outdoor environments. They protect the fiber core, cladding, and coating by enclosing everything within semi-rigid protective sleeves or tubes. In loose-tube cables that hold more than one optical fiber, each individually sleeved core is bundled loosely within an all-encompassing outer jacket.

Many loose-tube cables also have a water-resistant gel that surrounds the fibers. This gel helps protect them from moisture, so the cables are great for harsh, high-humidity environments where water or condensation can be a problem. The gel-filled tubes can expand and contract with temperature changes, too.

But gel-filled loose-tube cables are not the best choice when cable needs to be submerged or where it’s routed around multiple bends. Excess cable strain can force fibers to emerge from the gel.

Tight-buffered cables, in contrast, are optimized for indoor applications. Because they’re sturdier than loose-tube cables, they’re best suited for moderate-length LAN/WAN connections, long indoor runs, and even direct burial. Tight-buffered cables are also recommended for underwater applications.

Instead of a gel layer or sleeve to protect the fiber core, tight-buffered cables use a two-layer coating. One is plastic; the other is waterproof acrylate. The acrylate coating keeps moisture away from the cable, like the gel-filled sleeves do for loose-tube cables. But this acrylate layer is bound tightly to the plastic fiber layer, so the core is never exposed (as it can be with gel-filled cables) when the cable is bent or compressed underwater.

Tight-buffered cables are also easier to install because there’s no messy gel to clean up and they don’t require a fan-out kit for splicing or termination. You can crimp connectors directly to each fiber.

Want the best of both worlds? Try a hybrid, breakout-style fiber optic cable, which combines tight-buffered cables within a loose-tube housing. 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...Serial ATA technology.

Introduced in the mid 1980s, the Advanced Technology Attachment (ATA) interconnect soon became the industry-standard parallel input/output bus interface for connecting internal storage devices. Ultra ATA, which builds on the... more/see it noworiginal parallel ATA interface, has become the most commonly used type of interconnect.

But in recent years, sharing digital video and audio files over high-speed networks and other data-intensive uses has placed greater demands on hard drives, optical drives, and media-storage peripherals. So, not surprisingly, Ultra ATA now faces competition from a new technology—Serial ATA.

As the name implies, this new interconnect uses a serial bus architecture instead of a parallel one. Serial ATA currently supports speeds up to 150 MBps. Further enhancements could to boost rates as high as 600 MBps.

Compared with Ultra ATA, Serial ATA offers distinct advantages, including a point-to-point topology that enables you to dedicate 150 MBps to each connected device. Each channel can work independently and, unlike the “master-slave” shared bus of Ultra ATA, there’s no drive contention or interface bandwidth sharing.

Compared with Ultra ATA’s parallel bus design, Serial ATA requires a single signal path for sending data bits and a second path for receiving acknowledgement data. Each path travels across a 2-wire differential pair, and the bus contains four signal lines per channel. Fewer interface signals means the interconnect cable requires less board space.

Serial ATA also uses thinner cables (no more than 0.25" wide) that are available in longer lengths (up to 1 meter) as well as an improved connector design to reduce crosstalk. It also offers hot-swappable capabilities.

Although Serial ATA can’t interface directly with earlier Ultra ATA devices, it complies fully with the ATA protocol, so software between the two interconnects is compatible. collapse


Black Box Explains...Component video.

Traditional Composite video standards—NTSC, PAL, or SECAM—combine luminance (brightness), chrominance (color), blanking pulses, sync pulses, and color burst information into a single signal.

Another video standard—S-Video—separates luminance from chrominance to provide... more/see it nowsome improvement in video quality.

But there’s a new kind of video called Component video appearing in many high-end video devices such as TVs and DVD players. Component video is an advanced digital format that separates chrominance, luminance, and synchronization into separate signals. It provides images with higher resolution and better color quality than either traditional Composite video or S-Video. There are two kinds of Component video: Y-Cb-Cr and Y-Pb-Pr. Y-Cb-Cr is often used by high-end DVD players. HDTV decoders typically use the Y-Pb-Pr Component video signal.

Many of today’s high-end video devices such as plasma televisions and DVD players actually have three sets of video connectors: Composite, S-Video, and Component. The easiest way to improve picture quality on your high-end TV is to simply connect it using the Component video connectors rather than the Composite or S-Video connectors. Using the Component video connection enables your TV to make use of the full range of video signals provided by your DVD player or cable box, giving you a sharper image and truer colors.

To use the Component video built into your video devices, all you need is the right cable. A Component video cable has three color-coded BNC connections at each end. For best image quality, choose a high-quality cable with adequate shielding and gold-plated connectors. collapse

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