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Black Box Explains...How computer speeds are enhanced with PCI buses and UARTs.

The Peripheral Component Interconnect (PCI®) Bus enhances both speed and throughput. The PCI Local Bus is a high-performance bus that provides a processor-independent data path between the CPU and high-speed... more/see it nowperipherals. PCI is a robust interconnect interface designed specifically to accommodate multiple high-performance peripherals for graphics, full-motion video, SCSI, and LANs.

UARTs (Universal Asynchronous Receiver/ Transmitters) are integrated circuits that convert bytes from the computer bus into serial bits for transmission. By providing surplus memory in a buffer, UARTs help your applications overcome the factors that slow down your system. collapse


Screw Dimensions

Find the right screw length for your cabinet or rack.

Types of Screws

Screw Dimensions

There are two basic kinds of screws used for cabinets and racks—panhead screws and countersunk screws—and... more/see it nowthey’re measured in two different ways. Because the standard way to measure is from the tip of the business end of the screw to where the screw rests on the material it’s fastened to, a panhead screw is measured to the bottom of its head, whereas a countersunk screw is measured to the top of its head.
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Black Box Explains...Flexible microphones.

A headset featuring a flexible, swing-away microphone boom is easy to adjust—all you need to do is bend the boom until the microphone is in the correct position. Plus, you... more/see it nowcan easily swing the microphone out of your way if you wish to take a sip of coffee or soda while you’re on the phone. collapse


Black Box Explains... Manual switch chassis styles.

There are five manual switch chassis styles: three for standalone switches (Styles A, B, and C) and two for rackmount switches (Styles D and E). Below are the specifications for... more/see it noweach style.

Standalone Switches

Chassis Style A
Size — 2.5"H x 6"W x 6.3"D (6.4 x 15.2 x 16 cm
Weight — 1.5 lb. (0.7 kg)
Chassis Style B
Size — 3.5"H x 6"W x 6.3"D (8.9 x 15.2 x 16 cm)
Weight — 1.5 lb. (0.7 kg)
Chassis Style C
Size — 3.5"H x 17"W x 5.9"D (8.9 x 43.2 x 15 cm)
Weight — 8.4 lb. (3.8 kg)

Rackmount Switches

Chassis Style D (Mini Chassis)
Size — 3.5"H x 19"W x 5.9"D (8.9 x 48.3 x 15 cm)
Chassis Style E (Standard Chassis)
Size — 7"H x 19"W x 5.9"D (17.8 x 48.3 x 15 cm) collapse


Black Box Explains…Energy-Efficient Ethernet.

The IEEE 802.3az Ethernet standard, ratified in 2010, provides a standardized way for some Ethernet devices to reduce power consumption. Energy-Efficient Ethernet devices have a low-power idle (LPI) mode that... more/see it nowcan cut power use by 50% or more during periods of low data activity. Because energy-efficient Ethernet devices scale down power consumption when the load is lower, they save both the energy used to power processors and the energy used to cool them.

These energy savings are currently available for 100BASE-TX, 1000BASE-T, and 10GBASE-T Ethernet as well as some backplane Ethernet. 802.3az can be found on most types of network equipment, including NICs, switches, routers, and media converters. Because these devices are totally backwards compatible with other Ethernet devices, all you need to do to reap energy savings is to swap out devices. 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...LAN switches.



Rush hour-all day, every day.

Applications such as document imaging, video/multimedia production, and intranetworking are very demanding. They generate huge data files that often must be transferred... more/see it nowbetween stations based on strict timing requirements. If such traffic is not transmitted efficiently, you end up with jerky video, on-screen graphics that take forever to load, or other irritating, debilitating problems.


These problems arise because in traditional LANs, only one network node transmits data at a time while all other stations listen. This works in conventional, server-based LANs where multiple workstations share files or applications housed on a central server. But if a network has several servers, or if it supports high-bandwidth, peer-to-peer applications such as videoconferencing, the one-station-at-a-time model just doesn’t work.


Ideally, each LAN workstation should be configured with its own dedicated LAN cable segment. But that’s neither practical nor affordable. A far more reasonable solution is a network designed to provide clear paths from each workstation to its destination on demand, whether that destination is another workstation or server.


These vehicles clear the lanes.

Unlike bridges and routers, which process data packets on an individual, first-come, first-served basis, switches maintain multiple, simultaneous data conversions among attached LAN segments.


From the perspective of an end-user workstation, a switched circuit appears to be a dedicated connection-a direct, full-speed LAN link to an attached server or other remote LAN node. Although this technique is somewhat different from what a LAN bridge or router does, switching hubs are based on similar technologies.




Which route will you choose?

Switching hubs that use bridging technologies are called Layer 2 switches-a reference to Layer 2 or the Data-Link Layer of the OSI Model. These switches operate using the MAC addresses in Layer 2 and are transparent to network protocols. Switches that use routing technologies are known as Layer 3 switches, referring to Layer 3—the Network Layer—of the OSI Model. These switches, like routers, represent the next higher level of intelligence in the hardware hierarchy. Rather than passing packets based on MAC addresses, these switches look into the data structure and route it based on the network addresses found in Layer 3. They are also dependent on the network protocol.


Layer 2 switches connect different parts of the same network as determined by the network number contained with the data packet. Layer 3 switches connect LANs or LAN segments with different network numbers.


If you’re subdividing an existing LAN, obviously you’re dealing with only one network and one network number, so you can install a Layer 2 switch wherever it will segment network traffic the best, and you don’t have to reconfigure the LAN. However, if you use a Layer 3 switch, you’ll have to reconfigure the segments to ensure that each has a different network number.


Similarly, if you’re connecting existing networks, you have to examine the currently configured network numbers before adding a switch. If the network numbers are the same, you need to use a Layer 2 switch. If they’re different, you must use a Layer 3 switch.


When dealing with multiple existing networks, you’ll find they usually use different network numbers. In this case, it’s preferable to use a Layer 3 switch (or possibly even a full-featured router) to avoid reconfiguring the network.


But what if you’re designing a network from scratch and can choose either type of switch? Your decision should be based on the expected complexity of your LAN. Layer 3 routing technology is well suited for complex networks. Layer 2 switches are recommended for smaller, less complex networks.

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Black Box Explains...10-32, 12-24, and M6 rails.

The rails on cabinets and racks typically come with one of three mounting options: 10-32, 12-24, or M6.

The 10-32 and 12-24 options are round holes found on drilled and tapped... more/see it nowrails. You’ll find 10-32 openings on cabinets, while 12-24 holes are more commonly found on relay racks and frames. However, exceptions do exist. It’s very important to find out which type of mounting option your equipment requires before you order a cabinet or rack.

M6 holes are square, rather than round. M6 rails were developed to hold rackmount equipment, and you will find them on most server cabinets.

What makes M6 rails so popular on server cabinets? They’re adaptable. With just one cage nut, you can change a square hole into a round one. That gives you much more versatility in your equipment and mounting choices.

If you have a wide array of equipment, such as rackmount servers, hubs, routers, and patch panels, your best bet is a cabinet with M6 rails. It will accommodate the rackmount servers, and the other equipment can be mounted on those same rails using cage nuts.

If you’re unsure what type of cabinet, rack, or frame is best for your application, contact the experts at Black Box Tech Support. They’ll be glad to help you find the right enclosure for your equipment. collapse


Black Box Explains... G.703.

G.703 is the ITU-T recommendation covering the 4-wire physical interface and digital signaling specification for transmission at 2.048 Mbps (E1). G.703 also includes specifications for U.S. 1.544-Mbps T1 but is... more/see it nowstill generally used to refer to the European 2.048-Mbps transmission interface. 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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