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

The Digital Visual Interface (DVI) 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 a... more/see it nowlow level to create transitions that convey data. To minimize the number of transitions 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.

There are different types of DVI connectors: DVI-D, DVI-I, DVI-A, DFP, and EVC. DVI-D is a digital-only connector.

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. 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... Plasma vs. LCD Screens

When deciding whether to use plasma or liquid crystal diode (LCD) displays for your applications, you need to consider many factors. Both provide brilliant color, sharp text contrast, and crystal-clear... more/see it nowimages. But the way in which plasma and LCD screens process and display incoming video/computer signals is markedly different.

Compare and contrast.
Both plasma and LCD technology provide stark enough contrasts to make displays sharp and pleasing. But when it comes to contrast output, plasma technology outperforms LCD screens. Some plasma displays have a 3000:1 contrast ratio, which is the measure of the blackest black compared to the whitest white. LCDs use electric charges to untwist liquid crystals, thereby blocking light and emitting darker pixels. Despite this process, LCD displays don’t produce more than a 1000:1 contrast ratio.

Clarity that’s light waves ahead.
Pixels contain enough information to produce every color in the spectrum. Because plasmas use each and every pixel on their screens, color information is reproduced more accurately. Plasma screens display moving images with remarkable clarity, though burn-in can be an issue. For displays with lots of light and dark imagery, plasma panels provide excellent performance with their high-contrast levels, color saturation, and overall brightness.

LCD displays, on the other hand, manipulate light waves and reproduce colors by subtracting colors from white light. Though this makes it more difficult to maintain color accuracy and vibrancy compared to plasma screens, LCDs have an advantage with their higher-than-average number of pixels per square inch. These additional pixels make LCD technology better at displaying static images from computers or VGA sources in full-color detail. Plus, there’s no flicker and very little screen burn-in.

Applications with large amounts of data—such as those found on spreadsheets—display particularly well on LCD monitors.

Brilliant displays that go on and on.
With LCD screens, there are essentially no parts to wear out. LCD screens last as long as their backlights do, with displays lasting, on average, 50,000–75,000 hours. That’s why LCD screens are especially good for long-term applications, such as digital signage or displays that require around-the-clock use.

Plasma screens, however, use a combination of electric currents and noble gases (argon, neon, and xenon) to produce a glow, which in turn yields brilliant color. The half-life of these gases, however, is only around 25,000 hours. The glow they produce grows dimmer over time.

The right angle can make all the difference.
Plasmas light every pixel on the screen, making the brightness on the screen consistent and giving plasmas the edge when it comes to viewing angles. In fact, plasma screens have as much as a 160° viewing angle compared to LCDs. This makes viewing the images on the screen easier to see from a variety of angles. In doing so, however, plasmas consume much more power.

LCDs display at 130–140° angles, but their use of fluorescent backlighting requires much less power to operate than plasmas. This also makes LCDs less prone to burn-in or ghosting of images.
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Black Box Explains...Remote power control.

Simply put, remote power control is the ability to reset or reboot PC, LAN, telecom, and other computer equipment without being at the equipment’s location.

Who needs remote power control?... more/see it nowAny organization with a network that reaches remote sites. This can include branch offices, unmanned information kiosks, remote monitoring stations, alarm and control systems, and even HVAC systems.

When equipment locks up at remote sites, it is usually up to the system manager at headquarters to reset it. Often, there aren’t any technically trained personnel at the remote site who can perform maintenance and resets on equipment. So, in order to save traveling time and minimize downtime, remote power control enables the system manager to take care of things at the office without ever leaving home!

Remote power control can be done with modems or existing or special phone lines. The ideal system uses “out-of-band management,“ an alternate path over an ordinary dialup line that doesn’t interfere with network equipment.

An effective remote power control system incorporates the following:
• An existing phone line, such as a line being used for a fax, modem, or phone.
• Transparent operation. The system shouldn’t interfere with or be affected by normal calls.
• Security features. The system should prevent unauthorized access to network equipment.
• Flexibility. System managers should be able to dial in from anywhere and control mulitple devices with one call.
• Have power control devices that meet UL® and FCC requirements. collapse


Black Box Explains... SCSI termination

Passive termination
This is the oldest method of termination. A passive terminator sits on the bus to minimize reflections at the end of the cable. Passive terminators simply provide impedance close... more/see it nowto that of the cable. The terminator is “passive” because it doesn’t do any work to regulate power for termination; it relies on the interface card to provide steady power.

Active termination
This is a more stable form of terminating SCSI cables. Active terminators control the impedance at the end of the SCSI bus by using a voltage regulator, not just the power supplied by the interface card.

Forced-perfect termination
Of all SCSI terminators, this is the most complex. A cable with a forced-perfect terminator can actually change its impedance to compensate for variations along the bus. Forced-perfect terminators force the impedance of the cable to match each device through diode switching and biasing. collapse


Black Box Explains...Giga, Giga2, and Giga Plus—what you need to know.

Our Giga, Giga2, and Giga Plus and systems feature jacks, wallplates, surface-mount boxes, and other accessories. Components of each system are designed to work together. And they all work with... more/see it nowour GigaTrue® CAT6 and GigaBase® CAT5e cable. Here are the differences between the systems so you can make the right decision when choosing hardware.

Giga

  • Giga products are our original line of jacks, wallplates, etc.
  • Giga products, such as jacks and wallplates, are designed to work with Giga products.
  • To meet the needs of existing Giga systems, we continue to carry Giga products.

  • Giga2
  • Giga2 products are a newer line. They offer the same quality but are priced economically.
  • Giga2 products, such as jacks and wallplates, are designed to work with Giga2 products.

  • Giga Plus
  • Giga Plus is our newest line and is entirely made in the U.S. So if you need to buy American-made products, choose this line.
  • Giga Plus products are designed to work with Giga2 products.
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    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


    Black Box Explains...How MicroRACK Cards fit together.

    Slide a function card into the front of the rack. Then slide a connector card in from the back. The rest is simple. Just press the cards together firmly inside... more/see it nowthe rack to seat the connectors.

    Changing systems? It’s easy to change to a different connector card. Just contact us, and we’ll find the right connection for you.

    Add a hot-swappable power supply (AC for normal operation, VDC for battery-powered sites), and you’re up and running. 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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    DisplayPort cable.

    DisplayPort is a digital video interface that was designed by the Video Electronics Standards Association (VESA) in 2006 and has been produced since 2008. It competes directly with HDMI®. Unlike... more/see it nowHDMI, however, DisplayPort is an open standard with no royalties.

    This digital interface is used primarily between a computer and a monitor or a high-definition television and is built into many computer chipsets produced today. It’s incredibly versatile, with the capability to deliver digital video, audio, bidirectional communications, and accessory power over a single connector.

    DisplayPort v1.1 supports a maximum of 10.8 Gbps over a 2-meter cable; v1.2 supports up to 21.6 Gbps. DisplayPort v1.2 also enables you to daisychain up to four monitors with only a single output cable. It also offers the future promise of DisplayPort Hubs that would operate much like a USB hub.

    The standard DisplayPort connector is very compact and features latches that don’t add to the connector’s size. Unlike HDMI, a DisplayPort connector is easily lockable with a pinch-down locking hood, so it can't be easily dislodged. However, a quick squeeze of the connector releases the latch.

    DisplayPort supports cable lengths of up to 15 meters with maximum resolutions at cable lengths up to 3 meters. Bidirectional signaling enables DisplayPort to both send and receive data from an attached device.

    With the proper adapters, DisplayPort cable can carry DVI and HDMI signals, although this doesn’t work the other way around—DVI and HDMI cable can’t carry DisplayPort. Because DisplayPort can provide power to attached devices, DisplayPort to HDMI or DVI adapters don’t need a separate power supply.

    The Mini DisplayPort (MiniDP or mDP) is a miniatured version of the DisplayPort interface. It carries both digital and analog computer video and audio signals. Apple® introduced the Mini DisplayPort connector in 2008 and it is now on all new Mac® computers. It is also being used in newer PC notebooks. This small form factor connector fully supports the VESA DisplayPort protocol. It is particularly useful on systems where space is at a premium, such as laptops, or to support multiple connectors on reduced height add-in cards.

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