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Black Box Explains... Basic Printer Switches

Mechanical—A mechanical switch is operated by a knob or by push buttons and uses a set of copper or gold-plated copper contacts to make a connection. The internal resistance created... more/see it nowby this type of connection will affect your signal’s transmission distance and must be taken into account when calculating cable lengths.

Electronic—Although electronic switches are controlled by knobs and pushbuttons like mechanical switches, the switching is accomplished with electronic gates not mechanical contacts. Electronic switches don’t have the internal resistance of a mechanical switch—some even have the ability to drive signals for longer distances. And since they don’t generate electronic spikes like mechanical switches, they’re safe for sensitive components such as HP® laser printers. Some electronic switches can be operated remotely. collapse


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

The DVI (Digital Video Interface) technology is the standard digital transfer medium for computers while the HDMI interface is more commonly found on HDTVs, and other high-end displays.

The Digital... more/see it nowVisual Interface (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 is a digital-only connector for use between a digital video source and monitors. DVI-D eliminates analog conversion and improves the display. It can be used when one or both connections are DVI-D.
  • DVI-I (integrated) supports both digital and analog RGB connections. It can transmit either a digital-to-digital signals or an analog-to-analog signal. It is used by some manufacturers on products instead of separate analog and digital connectors. If both connectors are DVI-I, you can use any DVI cable, but a DVI-I is recommended.
  • DVI-A (analog) is used to carry an DVI signal from a computer to an analog VGA device, such as a display. If one or both of your connections are DVI-A, use this cable. ?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.
  • collapse


    Black Box Explains...How a line driver operates.

    Driving data? Better check the transmission.

    Line drivers can operate in any of four transmission modes: 4-wire full-duplex, 2-wire full-duplex, 4-wire half-duplex, and 2-wire half-duplex. In fact, most models support more... more/see it nowthan one type of operation.

    So how do you know which line driver to use in your application?

    The deal with duplexing.
    First you must decide if you need half- or full-duplex transmission. In half-duplex transmission, voice or data signals are transmitted in only one direction at a time, In full-duplex operation, voice or data signals are transmitted in both directions at the same time. In both scenarios, the communications path support the full data rate.

    The entire bandwidth is available for your transmission in half-duplex mode. In full-duplex mode, however, the bandwidth must be split in two because data travels in both directions simultaneously.

    Two wires or not two wires? That is the question.
    The second consideration you have is the type of twisted-pair cable you need to complete your data transmissions. Generally you need twisted-pair cable with either two or four wires. Often the type of cabling that’s already installed in a building dictates what kind of a line driver you use. For example, if two twisted pairs of UTP cabling are available, you can use a line driver that operates in 4-wire applications, such as the Short-Haul Modem-B Async or the Line Driver-Dual Handshake models. Otherwise, you might choose a line driver that works for 2-wire applications, such as the Short-Haul Modem-B 2W or the Async 2-Wire Short-Haul Modem.

    If you have the capabilities to support both 2- and 4-wire operation in half- or full-duplex mode, we even offer line drivers that support all four types of operation.

    As always, if you’re still unsure which operational mode will work for your particular applications, consult our Technical Support experts and they’ll help you make your decision. collapse


    Black Box Explains...Using repeaters to extend your network.

    A repeater is a signal regenerator. It amplifies and regenerates received data and relays data from one length of cable to another—this can be between two segments of the same... more/see it nowcable type (such as UTP to UTP) or between two lengths of entirely different cable types (such as UTP to ThinNet). Because repeaters operate at the Data Link layer of the OSI model, having too many repeaters on a network introduces delays and causes problems with signal timing. Ethernet allows a maximum of two IRLs (InterRepeater Links) between any two devices and up to four per network. A hub also counts as a repeater. (If simple media conversion is your goal, use media converters instead. For details, contact Tech Suport.)

    Repeaters boost distance by amplifying the signal.
    A repeater actually regenerates and amplifies the signal to gain distance. The repeater not only changes the media type, it also gives the signal a boost to send it over a longer distance.

    Repeaters boost distance through a change in media.
    In addition to amplifying the signal, a repeater can also add distance to your network by enabling you to change to a media type such as fiber that supports longer distances. collapse


    Black Box Explains...Speaker sound quality.

    A human with keen hearing can hear sounds within a range of about 20 Hz to 20 KHz. But most human speech is centered in the 1000 Hz range, so... more/see it nowmost old-fashioned analog telephone networks provided audio bandwidth only in this range. This range transmits most voice information but can fail to register voice subtleties and inflections.

    Because these older analog phone systems had such a narrow bandwidth, headset manufacturers built their products to operate only in those particular frequencies.

    When digital networks and fiber optic connections came into use, however, they provided a much wider bandwidth for voice transmission. This led to a corresponding increase in headset sound quality.

    Today, quality headsets take advantage of increased network bandwidth and typically can reproduce sounds in the 300 Hz to 3500 Hz range. This makes voices far easier to understand and enables you to pick up all the nuances and inflections of your caller’s voice. collapse


    Black Box Explains...MT-RJ fiber optic connectors.

    Bringing fiber to the desktop is a great way to provide your users with increased bandwidth. The first step in achieving this goal is to provide an inexpensive fiber optic... more/see it nowsystem that is intuitive to the end user, easy to terminate in the field, and widely supported by equipment manufacturers. MT-RJ could be the answer to all these requirements.

    A collaborative effort by leading fiber optic manufacturers, MT-RJ has an intuitive RJ latch that users recognize from copper Category 5 patch cords and traditional telephone cords, and it operates in the same way. The plug and jack are also similar in size to traditional RJ-type connectors.

    Field installation, a common concern, is easier because of MT-RJ’s no-polish, no-epoxy, quick-termination design. MT-RJ is available in single- or multimode configurations and is backwards compatible for integration into existing networks. Since MT-RJ has duplex polarity, you don’t have to worry about the polarity reversal that happens with traditional ST type connectors. The TIA/EIA recently voted to accept MT-RJ, indicating wide acceptance of the new design and possible future inclusion in the TIA/EIA 568A standard.

    Black Box, the name you trust to keep you up with the latest industry developments, supports this new technology. collapse


    Black Box Explains...Modem eliminators.

    Understanding the process of elimination.
    If your office environment has sync equipment, and if that equipment is also used for local data communications, you should consider replacing those modems with cost-effective... more/see it nowand versatile modem eliminators.

    What does a modem eliminator do?
    One modem eliminator can connect a local terminal and computer port in lieu of the pair of modems that they would normally connect to. Plus, a modem eliminator enables DCE-to-DTE data and control-signal connections that are not easily achieved by standard cables or connectors in a sync environment.

    Basically, a modem eliminator simulates a sync data link. It does this two ways. First, it provides clocking, which is mandatory for sync devices to communicate. Second, it provides the handshaking that DCEs do.

    Why should you use a modem eliminator?
    One—if you have two sync DTEs in the same room or close to each other, you will need a modem eliminator.

    Two—if you have a network with routers, you just found the perfect equipment tester.

    A modem eliminator can enable in-house bench testing of routers or existing equipment. There’s no need to place routers all over your network only to find out they don’t work once you test the LAN. A modem eliminator tells you what equipment passes your tests before you install.

    Three—a modem eliminator makes good economic sense. One does the job of two modems—and it does the job better. You get a high return on your investment. collapse


    Black Box Explains…Media converters that also work as switches.

    Media converters transparently convert the incoming electrical signal from one cable type and then transmit it over another type—thick coax to Thin, UTP to fiber, and so on. Traditionally, media... more/see it nowconverters were purely Layer 1 devices that only converted electrical signals and physical media and didn’t do anything to the data coming through the link.

    Today’s media converters, however, are often more advanced Layer 2 Ethernet devices that, like traditional media converters, provide Layer 1 electrical and physical conversion. But, unlike traditional media converters, they also provide Layer 2 services and route Ethernet packets based on MAC address. These media converters are often called media converter switches, switching media converters, or Layer 2 media converters. They enable you to have multiple connections rather than just one simple in-and-out connection. And because they’re switches, they increase network efficiency.

    Media converters are often used to connect newer 100-Mbps, Gigabit Ethernet, or ATM equipment to existing networks, which are generally 10BASE-T, 100BASE-T, or a mixture of both. They can also be used in pairs to insert a fiber segment into copper networks to increase cabling distances and enhance immunity to electromagnetic interference.

    Rent an apartment…
    Media converters are available in standalone models that convert between two different media types and in chassis-based models that house many media converters in a a single chassis.

    Standalone models convert between two media. But, like a small apartment, they can be outgrown.

    Consider your current and future applications before selecting a media converter. A good way to anticipate future network requirements is to choose media converters that work as standalone devices but can be rackmounted if needed later.

    …or buy a house.
    Chassis-based or modular media converter systems are normally rackmountable and have slots to house media converter modules. Like a well-planned house, the chassis gives you room to grow. These are used when many Ethernet segments of different media types need to be connected in a central location. Modules are available for the same conversions performed by the standalone converters, and they enable you to mix different media types such as 10BASE-T, 100BASE-TX, 100BASE-FX, ATM, and Gigabit modules. Although enterprise-level chassis-based systems generally have modules that can only be used in a chassis, many midrange systems feature modules that can be used individually or in a chassis. collapse


    Black Box Explains...50-micron vs. 62.5-micron fiber optic cable.

    The background
    As today’s networks expand, the demand for more bandwidth and greater distances increases. Gigabit Ethernet and the emerging 10 Gigabit Ethernet are becoming the applications of choice for current... more/see it nowand future networking needs. Thus, there is a renewed interest in 50-micron fiber optic cable.

    First used in 1976, 50-micron cable has not experienced the widespread use in North America that 62.5-micron cable has.

    To support campus backbones and horizontal runs over 10-Mbps Ethernet, 62.5 fiber, introduced in 1986, was and still is the predominant fiber optic cable because it offers high bandwidth and long distance.

    One reason 50-micron cable did not gain widespread use was because of the light source. Both 62.5 and 50-micron fiber cable can use either LED or laser light sources. But in the 1980s and 1990s, LED light sources were common. Since 50-micron cable has a smaller aperture, the lower power of the LED light source caused a reduction in the power budget compared to 62.5-micron cable—thus, the migration to 62.5-micron cable. At that time, laser light sources were not highly developed and were rarely used with 50-micron cable—mostly in research and technological applications.

    Common ground
    The cables share many characteristics. Although 50-micron fiber cable features a smaller core, which is the light-carrying portion of the fiber, both 50- and 62.5-micron cable use the same glass cladding diameter of 125 microns. Because they have the same outer diameter, they’re equally strong and are handled in the same way. In addition, both types of cable are included in the TIA/EIA 568-B.3 standards for structured cabling and connectivity.

    As with 62.5-micron cable, you can use 50-micron fiber in all types of applications: Ethernet, FDDI, 155-Mbps ATM, Token Ring, Fast Ethernet, and Gigabit Ethernet. It is recommended for all premise applications: backbone, horizontal, and intrabuilding connections, and it should be considered especially for any new construction and installations. IT managers looking at the possibility of 10 Gigabit Ethernet and future scalability will get what they need with 50-micron cable.

    Gaining ground
    The big difference between 50-micron and 62.5-micron cable is in bandwidth. The smaller 50-micron core provides a higher 850-nm bandwidth, making it ideal for inter/intrabuilding connections. 50-micron cable features three times the bandwidth of standard 62.5-micron cable. At 850-nm, 50-micron cable is rated at 500 MHz/km over 500 meters versus 160 MHz/km for 62.5-micron cable over 220 meters.

    Fiber Type: 62.5/125 µm
    Minimum Bandwidth (MHz-km): 160/500
    Distance at 850 nm: 220 m
    Distance at 1310 nm: 500 m

    Fiber Type: 50/125 µm
    Minimum Bandwidth (MHz-km): 500/500
    Distance at 850 nm: 500 m
    Distance at 1310 nm: 500 m

    As we move towards Gigabit Ethernet, the 850-nm wavelength is gaining importance along with the development of improved laser technology. Today, a lower-cost 850-nm laser, the Vertical-Cavity Surface-Emitting Laser (VCSEL), is becoming more available for networking. This is particularly important because Gigabit Ethernet specifies a laser light source.

    Other differences between the two types of cable include distance and speed. The bandwidth an application needs depends on the data transmission rate. Usually, data rates are inversely proportional to distance. As the data rate (MHz) goes up, the distance that rate can be sustained goes down. So a higher fiber bandwidth enables you to transmit at a faster rate or for longer distances. In short, 50-micron cable provides longer link lengths and/or higher speeds in the 850-nm wavelength. For example, the proposed link length for 50-micron cable is 500 meters in contrast with 220 meters for 62.5-micron cable.

    Migration
    Standards now exist that cover the migration of 10-Mbps to 100-Mbps or 1 Gigabit Ethernet at the 850-nm wavelength. The most logical solution for upgrades lies in the connectivity hardware. The easiest way to connect the two types of fiber in a network is through a switch or other networking “box.“ It is not recommended to connect the two types of fiber directly. 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

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