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Black Box Explains…Cooling blade servers.

Blade servers are hot. Really hot. These slim, high-powered CPUs generate heat like nothing you’ve ever installed in your data center before—a rack of blade servers can generate more heat... more/see it nowthan an electric oven! And as temperatures rise, servers may fail, leading to downtime and even data loss.

Needless to say, blade servers present a cooling challenge. If you plan to install them, you need to make sure you can accommodate their cooling needs.

Computer rooms have special equipment such as raised-floor cooling systems to meet their high cooling requirements, but it’s also important to ensure that cabinets used to house blade servers provide adequate ventilation—even in a cool room, hot spots can develop inside cabinets if air distribution is inadequate.

If you’re planning to install blade servers or other high-density components in cabinets, look for a cabinet with fully perforated doors in the front and rear— the greater the amount of perforation, the more cool air can be delivered to the components.

Don’t overload the cabinet by trying to fit in too many servers—75% to 80% of capacity is about right. Leave at least 1U of space between rows of servers for front-to-back ventilation. And finally, ensure all unused rack space is closed off with blank panels to prevent recirculation of warm air back to the front of the cabinet.

If you need help calculating your system’s cooling needs, contact our FREE Tech Support.
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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...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...Low-profile PCI serial adapters.

Ever notice that newer computers are getting smaller and slimmer? That means regular PCI boards won’t fit into these computers’ low-profile PCI slots. But because miniaturization is the rage in... more/see it nowall matters of technology, it was only a short matter of time before low-profile PCI serial adapters became available—and Black Box has them.

Low-profile cards meet the PCI Special Interest Group (PCI-SIG) Low-Profile PCI specifications, the form-factor definitions for input/output expansion. Low-Profile PCI has two card lengths defined for 32-bit bus cards: MD1 and MD2. MD1 is the smaller of the two, with cards no larger than 4.721 inches long and 2.536 inches high. MD2 cards are a maximum of 6.6 inches long and 2.536 inches high.

BLACK BOX® Low-Profile Serial PCI cards comply with the MD1 low-profile specification and are compatible with the universal bus. Universal bus is a PCI card that can operate in either a 5-V or 3.3-V signaling level system. collapse


Black Box Explains... Baseband, broadband, and carrierband transmissions.

Depending on the environment and how the electrical signal is sent over the cable, coax can be used for three types of transmissions.

Baseband transmissions use the entire communication channel capacity... more/see it nowto transmit a single data signal. Many LANs employ Thin coax for baseband signaling.

Broadband transmissions use different frequencies to carry several analog signals simultaneously. Each signal can for be a different type of information—data, voice, even video. Broadband transmissions over coax employ either one or two cables. With single-cable coax wiring, frequencies are split into individual channels for each station; some channels are allocated for bidirectional communication. Dual-cable coax wiring uses one cable for sending and one cable for receiving data, each with multiple channels. Broadband transmissions are ideal for long distances. Thick coax is often used for broadband transmissions.

Unlike broadband transmissions, carrierband transmissions can only use one information channel. Carrierband is best suited for the horizontal subsystems (subnetworks) in industrial settings. Many LANs use Thin coax for carrierband signaling. collapse


Black Box Explains...DIN rail usage.

DIN rail is an industry-standard metal rail, usually installed inside an electrical enclosure, which serves as a mount for small electrical devices specially designed for use with DIN rails. These... more/see it nowdevices snap right onto the rails, sometimes requiring a set screw, and are then wired together.

Many different devices are available for mounting on DIN rails: terminal blocks, interface converters, media converter switches, repeaters, surge protectors, PLCs, fuses, or power supplies, just to name a few.

DIN rails are a space-saving way to accommodate components. And because DIN rail devices are so easy to install, replace, maintain, and inspect, this is an exceptionally convenient system that has become very popular in recent years.

A standard DIN rail is 35 mm wide with raised-lip edges, its dimensions outlined by the Deutsche Institut für Normung, a German standardization body. Rails are generally available in aluminum or steel and may be cut for installation. Depending on the requirements of the mounted components, the rail may need to be grounded. collapse


Black Box Explains...Choosing a wireless antenna.


Ride the wave.

One of the most critical components to operating a successful wireless network is having the right antennas. Antennas come in many different shapes and sizes,... more/see it noweach designed for a specific function. Selecting the right antennas for your network is crucial to achieving optimum network performance. In addition, using the right antennas can decrease your networking costs since you’ll need fewer antennas and access points.


Basically, a wireless network consists of data, voice, and video information packets being transmitted over low-frequency radio waves instead of electrically over copper cable or via light over fiber lines. The antenna acts as a radiator and transmits waves through the air, just like radio and TV stations. Antennas also receive the waves from the air and transport them to the receiver, which is a radio, TV, or in the case of wireless networking, a router or an access point.


Type cast.

The type of antennas you use depends on what type of network you’re setting up and the coverage you need. How large is your network? Is it for a home, single office, campus, or larger? Is it point-to-point or multipoint?


The physical design-walls, floors, etc.- of the building(s) you’re working in also affects the type and number of antennas you need. In addition, physical terrain affects your antenna choices. Obviously, a clear line of sight works best, but you need to consider obstructions such as trees, buildings, hills, and water. (Radio waves travel faster over land than water.) You even need to consider traffic noise in urban settings.


The ideal shape.

Let’s take a look at the different types of antennas.


Isotropic Antenna. First, think of the introduction to the old RKO movies. A huge tower sits on top of the world and emanates circular waves in all directions. If you could actually see the waves, they would form a perfect sphere around the tower. This type of antenna is called an isotropic antenna, and does not exist in the real world. It is theoretical and is used as a base point for measuring actual antennas.


Go in the right direction.

Now let’s turn to real-world antennas. There are many types of antennas that emit radio waves in different directions, shapes, and on different planes. Think of the spherical isotropic antenna. If squeezed from the sides, it will become shaped like a wheel and will concentrate waves on a vertical plane. If squeezed from the top, it will flatten out like a pancake and radiate waves on a horizontal plane. Thus, there are two basic types of antennas: directional and omnidirectional.


Directional antennas.

Directional antennas, primarily used in point-to-point networks, concentrate the waves in one direction much like a flashlight concentrates light in a narrow beam. Directional antennas include backfire, Yagi, dish, panel, and sector.


Backfire. This small directional antenna looks like a cake pan with a tin can in the middle. It’s designed to be compact, often under 11" in diameter, making it unobtrusive and practical for outdoor use. These antennas also offer excellent gain, and can be used in both point-to-point or point-to-multipoint systems.


Yagi. The Yagi-Uda (or Yagi) antenna is named for its Japanese inventors. The antenna was originally intended for radio use and is now frequently used in 802.11 wireless systems.


A Yagi antenna is highly directional. It looks like a long fishbone with a central spine and perpendicular rods or discs at specified intervals. Yagi antennas offer superior gain and highly vertical directionality. The longer the Yagi, the more focused its radiation is. Many outdoor Yagi antennas are covered in PVC so you can’t see the inner structure.


Yagi antennas are good for making point-to-point links in long narrow areas (for instance, connecting to a distant point in a valley) or for point-to-point links between buildings. They can also be used to extend the range of a point-to-multipoint network.


Parabolic or Dish. These antennas look like a circular or rectangular concave bowl or "dish". The backboard can be solid or a grid design. Parabolic grid designs are excellent for outdoor use since the wind blows right through them. The concave nature of this dish design focuses energy into a narrow beam that can travel long distances, even up to several miles. This makes parabolic antennas ideal for point-to-point network connections. Since they generate a narrow beam in both the horizontal and vertical planes, offer excellent gain, and minimize interference, they’re ideal for long-distance point-to-point networks.


Panel or Patch. These antennas are often square or rectangular, and they’re frequently hung on walls. They’re designed to radiate horizontally forward and to the side, but not behind them. Sometimes they’re called "picture-frame" antennas.


Panel antennas are ideal in applications where the access point is at one end of a building. They’re good for penetrating a single floor of a building, and for small and medium-size homes and offices. Since they might not have much vertical radiation, they might not be a good choice for multifloor applications.


Because panel antennas can be easily concealed, they’re a good choice when aesthetics are important.


Sector. A sector antenna can be any type of antenna that directs the radio waves in a specific area. They are often large, outdoor flat-panel or dish-type antennas mounted up high and tilted downward toward the ground. These antennas are often used in sprawling campus settings to cover large areas.


Omnidirectional antennas.

Omnidirectional antennas provide the widest coverage possible and are generally used in point-to-multipoint networks. Their range can be extended by overlapping circles of coverage from multiple access points. Most omnidirectional antennas emanate waves in a fan-shaped pattern on a horizontal plane. Overall, omnidirectional antennas have lower gain than directional antennas. Examples of omnidirectional antennas include: integrated, blade, and ceiling.


Integrated. Integrated antennas are antennas that are built into wireless networking devices. They may be embedded in PC card client adapters or in the covers or body of laptops or other devices, such as access points. Integrated antennas often do not offer the same reception as external antennas and might not pick up weak signals. Access points with integral antennas must often be moved or tilted to get the best reception.


Blade. These small, omnidirectional antennas are often housed in long, thin envelopes of plastic. They are most often used to pick up a signal in a low-signal or no-signal spot. You usually will see them on the walls of cubicles, mounted on desktops, or even hung above cubicles to catch signals. They’re basically an inexpensive signal booster.


Ceiling Dome. These are sometimes also called ceiling blister antennas. They look somewhat like a smoke detector and are designed for unobtrusive use in ceilings, particularly drop ceilings. Ceiling dome antennas often have a pigtail for easy connection to access points. They’re excellent for use in corporate environments where wide coverage over a cube farm is needed.


Wave basics.

To better understand wireless antennas and networking, there are some basic measurements and terms that need to be discussed.


Gain. One of the primary measurements of antennas is gain. Gain is measured as dBi, which is how much the antenna increases the transmitter’s power compared to the theoretical isotropic antenna, which has a gain of 0 dBi. dBi is the true gain the antenna provides to the transmitter’s output. Gain is also reciprocal-it’s the same transmitting and receiving. Higher gain means stronger sent and received signals. An easy way to remember gain basics is that every 3 dB of gain added doubles the effective power output of an antenna. The more an antenna concentrates a signal, the higher the gain it will have.


You can actually calculate the gains and losses of a system by adding up the gains and losses of its parts in decibels.


Frequency and Wavelength. Electromagnetic waves are comprised of two components: frequency and wavelength.


Frequency is how many waves occur each second. Wavelength is the distance between one peak of a wave and the next peak. Lower frequencies have longer wavelengths; higher frequencies have shorter wavelengths. For example, the frequency of AM radio is 1 MHz with a wavelength of about 1000 feet. FM radios operate at a much higher frequency of 100 MHz and have a wavelength of about 100 feet.


The two most common frequencies for wireless networking are 2.4-GHz and 5-GHz. Both are very high frequencies with very short wavelengths in the microwave band. The 2.4-GHz frequency has a wavelength of about 5 inches.


Beamwidth. Consider an antenna to be like a flashlight or spotlight. It reflects and directs the light (or radio waves) in a particular direction. Beamwidth actually measures how energy is focused or concentrated.


Polarization. This is the direction in which the antenna radiates wavelengths, either vertically, horizontally, or circularly. Vertical antennas have vertical polarization and are the most common. For optimum performance, it is important that the sending and receiving antennas have the same polarization.


VSWR and Return Loss. Voltage Standing Wave Ratio (VSWR) measures how well the antenna is matched to the network at the operating frequency being used. It indicates how much of the received signal won’t reach either the transceiver or receiver. Return loss measures how well matched an antenna is to the network. Typical VSWR numbers are 1:1.2 or 1:1.5. A typical return loss number is 20.

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Black Box Explains...Connectors.



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Black Box Explains...Choosing SCSI cables.

1. Quality. Your system’s performance depends on the quality of your SCSI cables. Without high-quality cables specifically designed for SCSI applications, you could be jeopardizing your SCSI lifeline. Inferior cables,... more/see it nowadapters, and terminators can cause random errors, data corruption, or even a system crash! Black Box® SCSI Cables and components are the absolute best-quality products. And they’re guaranteed for life.

2. Length. For peak network performance, make sure your cables are the right length. As cable runs get longer, signals weaken and are more susceptible to noise. Always use the shortest cable for the task. And stay within the SCSI-1 and SCSI-2 standards of six meters or three meters for Fast SCSI. Remember, this is the total length of the bus, including all internal and external cables. collapse


Black Box Explains...Virtual LANs (VLANs).

True to their name, VLANs are literally “virtual“ LANs—mini subLANs that, once configured, can exist and function logically as single, secure network segments, even though they may be part of... more/see it nowa much larger physical LAN.

VLAN technology is ideal for enterprises with far-reaching networks. Instead of having to make expensive, time-consuming service calls, system administrators can configure or reconfigure workstations easily or set up secure network segments using simple point-and-click, drag-and-drop management utilities. VLANs provide a way to define dynamic new LAN pathways and create innovative virtual network segments that can range far beyond the traditional limits of geographically isolated workstation groups radiating from centralized hubs.

For instance, using VLAN switches, you can establish a secure VLAN made up of select devices located throughout your enterprise (managers’ workstations, for example) or any other device that you decide requires full access to the VLAN you’ve created.

According to Cisco, a VLAN is a switched network logically segmented by functions, project teams, or applications regardless of the physical location of users. You can assign each switch port to a different VLAN. Ports configured in the same VLAN share broadcasts; ports that don’t belong to the VLAN don’t share the data.

VLAN switches group users and ports logically across the enterprise—they don’t impose physical constraints like in a shared-hub architecture. In replacing shared hubs, VLAN switches remove the physical barriers imposed by each wiring closet.

To learn more about smart networking with VLANs, call the experts in our Local Area Network Support group at 724-746-5500, press 1, 2, 4. collapse

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