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Black Box Explains... PCI buses

A Peripheral Component Interconnect (PCI) Bus enhances both speed and throughput. A 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. 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...NEBS Level 3.

Network Equipment Building System (NEBS) standards set requirements for telco equipment. The standards are maintained by Telcordia Technologies, Inc., formerly Bellcore. Bellcore Special Report, SR-3580 defines three distinct functional levels... more/see it nowof NEBS compliance. The third of these levels, NEBS Level 3, is the most stringent, certifying carrier-class equipment intended for long-term use in variable environments.

NEBS Level 3 certifies that a piece of equipment can be safely used in an extreme environment. To become certified at NEBS Level 3, a device must meet strict physical, electrical, and environmental requirements to prove it will operate safely and reliably in extreme conditions. It must pass a series of tests that include extreme heat, humidity, fire, earthquakes (Zone 4), light, and noise. collapse


Black Box Explains...Advantages of fiber optic line drivers.

Fiber optic line drivers are much better for communications than copper-wire alternatives because they offer three main advantages: superior conductivity, freedom from interference, and security.

Superior conductivity for increased performance
The glass... more/see it nowcore of a fiber optic cable is an excellent signal conductor. With proper splices and terminations, fiber cable yields very low signal loss and can easily support data rates of 100 Mbps or more.

Immunity to electrical interference
Because fiber optic line drivers use a nonmetallic conductor, they don’t pick up or emit electromagnetic or radio-frequency interference (EMI/RFI). Crosstalk (interference from an adjacent communication channel) is also eliminated, which increases transmission quality.

Signals transmitted via fiber optic line drivers aren’t susceptible to any form of external frequency-related interference. That makes fiber connections completely immune to damaging power surges, signal distortions from nearby lightning strikes, and high-voltage interference. Because fiber cable doesn’t conduct electricity, it can’t create electrical problems in your equipment.

Signal security
Electronic eavesdropping requires the ability to intercept and monitor the electromagnetic frequencies of signals traveling over a copper data wire. Fiber optic line drivers use a light-based transmission medium, so they’re completely immune to electronic bugging. collapse


Black Box Explains...Ethernet.



If you have an existing network, there’s a 90% chance it’s Ethernet. If you’re installing a new network, there’s a 98% chance it’s Ethernet—the Ethernet standard is... more/see it nowthe overwhelming favorite network standard today.


Ethernet was developed by Xerox®, DEC®, and Intel® in the mid-1970s as a 10-Mbps (Megabits per second) networking protocol—very fast for its day—operating over a heavy coax cable (Standard Ethernet).


Today, although many networks have migrated to Fast Ethernet (100 Mbps) or even Gigabit Ethernet (1000 Mbps), 10-Mbps Ethernet is still in widespread use and forms the basis of most networks.


Ethernet is defined by international standards, specifically IEEE 802.3. It enables the connection of up to 1024 nodes over coax, twisted-pair, or fiber optic cable. Most new installations today use economical, lightweight cables such as Category 5 unshielded twisted-pair cable and fiber optic cable.


How Ethernet Works

Ethernet signals are transmitted from a station serially, one bit at a time, to every other station on the network.


Ethernet uses a broadcast access method called Carrier Sense Multiple Access/Collision Detection (CSMA/CD) in which every computer on the network “hears” every transmission, but each computer “listens” only to transmissions intended for it.


Each computer can send a message anytime it likes without having to wait for network permission. The signal it sends travels to every computer on the network. Every computer hears the message, but only the computer for which the message is intended recognizes it. This computer recognizes the message because the message contains its address. The message also contains the address of the sending computer so the message can be acknowledged.


If two computers send messages at the same moment, a “collision” occurs, interfering with the signals. A computer can tell if a collision has occurred when it doesn’t hear its own message within a given amount of time. When a collision occurs, each of the colliding computers waits a random amount of time before resending the message.


The process of collision detection and retransmission is handled by the Ethernet adapter itself and doesn’t involve the computer. The process of collision resolution takes only a fraction of a second under most circumstances. Collisions are normal and expected events on an Ethernet network. As more computers are added to the network and the traffic level increases, more collisions occur as part of normal operation. However, if the network gets too crowded, collisions increase to the point where they slow down the network considerably.


Standard (Thick) Ethernet (10BASE5)


  • Uses “thick” coax cable with N-type connectors for a backbone and a transceiver cable with 9-pin connectors from the transceiver to the NIC.
  • Both ends of each segment should be terminated with a 50-ohm resistor.
  • Maximum segment length is 500 meters.
  • Maximum total length is 2500 meters.
  • Maximum length of transceiver cable is 50 meters.
  • Minimum distance between transceivers is 2.5 meters.
  • No more than 100 transceiver connections per segment are allowed.
Thin Ethernet (ThinNet) (10BASE2)


  • Uses "Thin" coax cable.
  • The maximum length of one segment is 185 meters.
  • The maximum number of segments is five.
  • The maximum total length of all segments is 925 meters.
  • The minimum distance between T-connectors is 0.5 meters.
  • No more than 30 connections per segment are allowed.
  • T-connectors must be plugged directly into each device.
Twisted-Pair Ethernet (10BASE-T)


  • Uses 22 to 26 AWG unshielded twisted-pair cable (for best results, use Category 4 or 5 unshielded twisted pair).
  • The maximum length of one segment is 100 meters.
  • Devices are connected to a 10BASE-T hub in a star configuration.
  • Devices with standard AUI connectors may be attached via a 10BASE-T transceiver.
Fiber Optic Ethernet (10BASE-FL, FOIRL)


  • Uses 50-, 62.5-, or 100-micron duplex multimode fiber optic cable (62.5 micron is recommended).
  • The maximum length of one 10BASE-FL (the new standard for fiber optic connections) segment is 2 kilometers.
  • The maximum length of one FOIRL (the standard that preceded the new 10BASE-FL) segment is 1 kilometer.
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Black Box Explains...Thermocouples

A thermocouple is a device that measures temperature by using the fact that a junction between two different metals produces a varying voltage related to their temperature. Two common types... more/see it nowof thermocouple are Type J and Type K.

Type J thermocouples use iron paired with a nickel-copper alloy. Type J thermocouples may cover a temperature range of up to -40 to +1382° F (-40 to +750°C), and offer high sensitivity.

Type K, the most common type of thermocouple, uses nickel-chromium and nickel-aluminum alloys. Because Type K is an early specification, its characteristics vary widely; individual thermocouples may cover a range of up to -328 to +2462 °F (-200 to +1350 °C). collapse


Black Box Explains…SFP compatibility.

Standards for SFP fiber optic media are published in the SFP Multi-Source Agreement, which specifies size, connectors, and signaling for SFPs, with the idea that all SFPs are compatible with... more/see it nowdevices that have appropriate SFP slots. These standards, which also extend to SFP+ and XFP transceivers, enable users to mix and match components from different vendors to meet their own particular requirements.

However, some major manufacturers, notably Cisco®, HP®, and 3Com®, sell network devices with SFP slots that lock out transceivers from other vendors. Because the price of SFPs—especially Gigabit SFPs and 10GBASE SFP+ and XFP transceivers—can add significantly to the price of a switch, this lock-out scheme raises hardware costs and limits transceiver choices.

Many vendors don’t advertise that SFP slots on their devices don’t accept standard SFPs from other vendors. This can lead to unpleasant surprises when a device simply refuses to communicate with an SFP.

Another game that some vendors play is to build devices that accept open-standard SFPs, but refuse to support those devices when SFPs from another vendor are used with them.

The only way around this “lock-in” practice is to only buy network devices that accept standard SFPs from all vendors and to buy from vendors that support their devices no matter whose SFPs are used with them. Questions? Call our FREE Tech Support at 724-746-5500. collapse


Black Box Explains...Choosing a cabinet.

Understanding cabinet and rack measurements.
The main component of a cabinet is a set of vertical rails with mounting holes to which you attach your equipment or shelves. When you consider... more/see it nowthe width or height of a cabinet, clarify whether the dimensions are inside or outside.

The first measurement you need to know is the width of the rails. The most common size is 19 inches with hole-to-hole centers measuring 18.3 inches. There are also 23-inch and 24-inch cabinets and racks. Most rackmount equipment is made to fit 19-inch rails but can be adapted for wider rails.

After width, the most important specification is the number of rack units, abbreviated as “U.” It’s a measurement of space available to mount equipment. Because cabinet width is standard, the amount of space is what determines how much equipment you can actually install. Remember, this is an internal measurement of usable space and is smaller than an external measure of the cabinet or rack.

One rack unit (1U) is 1.75 inches of usable space and is usually, but not always, measured vertically. So, for example, a rackmount device that’s 2U high takes up 3.5 inches of rack space. A rack that’s 20U high has 35 inches of usable space.

Choosing the right cabinet.
Here’s a quick checklist of features to keep in mind before you choose a cabinet for servers or other network devices:
• High-volume airflow.
• Adjustable rails.
• Rails with M6 square holes.
• Moisture and dust resistance.
• Air filters.
• Front and/or rear accessibility.
• Locking doors.
• Left- or right-hinging doors.
• Power strips and cable organizers.
• Interior lighting.
• Preassembly.
• Availability of optional shelves, fans, and casters.
• Cable management rails, space, and knockouts.
• Extra depth to accommodate newer, deeper servers.

Don’t forget to accessorize.
Even if your cabinet is in a climate-controlled room, you may need to add a fan panel to help keep your equipment from overheating. It’s especially important to have ventilation in an enclosed cabinet.

Rackmount power strips mount either vertically or horizontally. Some have widely spaced outlets to accommodate transformer blocks. Some power strips include surge protection.

Mission-critical equipment should be connected to an uninterruptible power supply (UPS). A UPS keeps your equipment from crashing during a brief blackout or brownout and provides you with enough time to shut down everything properly in a more extended power outage.

For accessories that make cabling easier, just take a look at our many cable management products. We have cable management guides, rackmount raceways, horizontal and vertical organizers, cable managers, cable hangers, and much more. collapse


Black Box Explains...Types of KVM switches.

Black Box has the keyboard/video switches you need to share one CPU between several workstations or to control several CPUs from one monitor and keyboard.

If you do a lot of... more/see it nowswitching, you need premium switches—our top-of-the-line ServSwitch™ KVM switches give you the most reliable connections for the amount of KVM equipment supported. With ServSwitch KVM switches, you can manage as many CPUs as you want from just one workstation, and you can access any server in any computer room from any workstation. Eliminating needless equipment not only saves you money, it also gives you more space and less clutter. Plus, you can switch between PCs, Sun®, and Mac® CPUs. ServSwitch KVM switches can also cut your electricity and cooling costs because by sharing monitors, you use less power and generate less heat.

If your switching demands are very minor, you may not need products as advanced as ServSwitch. Black Box offers switches to fill less demanding needs. Most of these are manual switches or basic electronic switches, which don’t have the sophisticated emulation technology used by the ServSwitch.

For PCs with PS/2® keyboards, try our Keyboard/Video Switches. They send keyboard signals, so your CPUs boot up as though they each have their own keyboard.

With the RS/6000™ KVM Switch, you can run up to six RS/6000 servers from one workstation. Our Keyboard/ Video Switch for Mac enables you to control up to two Mac CPUs from one keyboard and monitor.

With BLACK BOX® KVM Switches, you can share a workstation with two or four CPUs. They’re available in IBM® PC and Sun Workstation® configurations.

You’ll also find that our long-life manual Keyboard/Video Switches are perfect for basic switching applications. collapse


Black Box Explains...UTP cable and color drift.

UTP cable is often used with video or KVM extenders to extend the reach of a video signal. It’s popular for this application because it’s lightweight, easy to handle, and... more/see it nowinexpensive. But when you transmit video over long stretches of twisted-pair cable, you sometimes run into a phenomenon called color drift or color split.

Color drift shows up as that annoying colored shadow you occasionally see around objects on a video screen. It sometimes happens with UTP cable because the pairs of wire in the cable are twisted at slightly different rates to reduce crosstalk between pairs. Because of these differences between wire pairs, video signals for different colors often travel different distances before they reach the remote receiver. When one color signal arrives behind the others because its wire is longer, you get that red, green, or blue shadow around the objects on your video screen.

UTP cable varies widely by manufacturer, so before installing video extenders, it’s difficult to determine whether or not you’re going to have a color drift problem. You’re more likely to experience color drift with higher grades (CAT5e or CAT6) of cable, on longer cable runs, and on high-resolution screens.

If you experience color drift, there are several possible solutions. You can use a shorter length of cable, switch from CAT5e or CAT6 cable to CAT5 cable, use a lower screen resolution, or use a video skew compensator.

A video skew compensator removes color drift by delaying some color signals to compensate for differences in wire pairs. collapse

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