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Black Box Explains...Dry Contacts

A dry contact, also called a volt-free contact, is a relay contact that does not supply voltage. The relay energizes or de-energizes when a change to its input has occurred.... more/see it nowIn other words, a dry contact simply detects whether or not an input switch is open or closed.

The dry contacts in the ServSensor Contact provide a simple two-wire interface that can be easily adapted to third-party sensors and devices. Because you define what the open or closed condition means, dry contacts are infinitely adaptable.

Use dry contacts to monitor alarms such as fire alarms, burglar alarms, and alarms on power systems such as UPSs. A very common use for dry contacts is to detect whether a cabinet door is open or closed. collapse


Black Box Explains...Remote access.

Remote access is the ability to access a network, a personal computer, a server, or other device from a distance for the purpose of controlling it or to access data.... more/see it nowToday, remote access is usually accomplished over the Internet, although a local IP network, telephone lines, cellular service, or leased lines may also be used. With today’s ubiquitous Internet availability, remote access is increasingly popular and often results in significant cost savings by enabling greater network access and reducing travel to remote sites. Remote access is a very general term that covers a wide range of applications from telecommuting to resetting a distant server. Here are just a few of the applications that fall under the remote access umbrella:

Remote network access
A common use for remote access is to provide corporate network access to employees who work at home or are in sales or other traveling positions. This kind of remote access typically uses IPsec VPN tunnels to authenticate and secure connections.

Remote desktop access
Remote desktop access enables users to access a computer remotely from another computer and take control of it as if it were local. This kind of remote control requires that special software—which is included with most operating systems—be installed and enabled. It’s often used by those who travel frequently to access their “home” computer, and by network administrators for remote server access. This remote access method has some inherent security concerns and is usually incompatible with firewalls, so it’s important to be aware of its limitations and use adequate security precautions.

Remote KVM access
A common application in organizations that maintain servers across multiple sites is server administration through an IP-enabled KVM switch. These IP-addressable switches support one or more servers and have an integral Web server, enabling users to access them over the Internet through a Web browser. Because they’re intended for Internet use, these switches offer authentication and encryption for secure connections.

Remote power management
Anyone who’s ever had to get out of bed in the middle of the night to go switch a server off and back on again to reset it can appreciate the convenience of remote power management. Remote power managers have a wide range of capabilities ranging from simple power switching to reboot a device to sophisticated power monitoring, reporting, and management functions.

Remote environmental security monitoring
Remote environmental and security monitoring over the Internet is increasingly popular, largely because of the cost savings of using existing network infrastructure rather than a proprietary security system. This application requires IP-addressable hubs that support a variety of sensors ranging from temperature and humidity to power monitors. Some models even support surveillance cameras. collapse


Black Box Explains...Fiber.


Fiber versus copper.

When planning a new or upgraded cabling infrastructure, you have two basic choices: fiber or copper. Both offer superior data transmission. The decision on which one... more/see it nowto use may be difficult. It will often depend on your current network, your future networking needs, and your particular application, including bandwidth, distances, environment, cost, and more. In some cases, copper may be a better choice; in other situations, fiber offers advantages.


Although copper cable is currently more popular and much more predominant in structured cabling systems and networks, fiber is quickly gaining fans.


Fiber optic cable is becoming one of the fastest-growing transmission mediums for both new cabling installations and upgrades, including backbone, horizontal, and even desktop applications. Fiber optic cable is favored for applications that need high bandwidth, long distances, and complete immunity to electrical interference. It’s ideal for high data-rate systems such as Gigabit Ethernet, FDDI, multimedia, ATM, SONET, Fibre Channel, or any other network that requires the transfer of large, bandwidth-consuming data files, particularly over long distances. A common application for fiber optic cable is as a network backbone, where huge amounts of data are transmitted. To help you decide if fiber is right for your new network or if you want to migrate to fiber, take a look at the following:



The advantages of fiber.

Greater bandwidth-Because fiber provides far greater bandwidth than copper and has proven performance at rates up to 10 Gbps, it gives network designers future-proofing capabilities as network speeds and requirements increase. Also, fiber optic cable can carry more information with greater fidelity than copper wire. That’s why the telephone networks use fiber, and many CATV companies are converting to fiber.


Low attenuation and greater distance-Because the fiber optic signal is made of light, very little signal loss occurs during transmission so data can move at higher speeds and greater distances. Fiber does not have the 100-meter (304.8-ft.) distance limitation of unshielded twisted-pair copper (without a booster). Fiber distances can range from 300 meters to 40 kilometers, depending on the style of cable, wavelength, and network. (Fiber distances are typically measured in metric units.) Because fiber signals need less boosting than copper ones do, the cable performs better.


Fiber networks also enable you to put all your electronics and hardware in one central location, instead of having wiring closets with equipment throughout the building.


Security-Your data is safe with fiber cable. It does not radiate signals and is extremely difficult to tap. If the cable is tapped, it’s very easy to monitor because the cable leaks light, causing the entire system to fail. If an attempt is made to break the security of your fiber system, you’ll know it.


Immunity and reliability-Fiber provides extremely reliable data transmission. It’s completely immune to many environmental factors that affect copper cable. The fiber is made of glass, which is an insulator, so no electric current can flow through. It is immune to electromagnetic interference and radio-frequency interference (EMI/RFI), crosstalk, impedance problems, and more. You can run fiber cable next to industrial equipment without worry. Fiber is also less susceptible to temperature fluctuations than copper is and can be submerged in water.


Design-Fiber is lightweight, thin, and more durable than copper cable. And, contrary to what you might think, fiber optic cable has pulling specifications that are up to ten times greater than copper cable’s. Its small size makes it easier to handle, and it takes up much less space in cabling ducts. Although fiber is still more difficult to terminate than copper is, advancements in connectors are making temination easier. In addition, fiber is actually easier to test than copper cable.


Migration-The proliferation and lower costs of media converters are making copper to fiber migration much easier. The converters provide seamless links and enable the use of existing hardware. Fiber can be incorporated into networks in planned upgrades.


Standards-New TIA/EIA standards are bringing fiber closer to the desktop. TIA/EIA-785, ratified in 2001, provides a cost-effective migration path from 10-Mbps Ethernet to 100-Mbps Fast Ethernet over fiber (100BASE-SX). A recent addendum to the standard eliminates limitations in transceiver designs. In addition, in June 2002, the IEEE approved a 10-Gigabit Ethernet standard.


Costs-The cost for fiber cable, components, and hardware is steadily decreasing. Installation costs for fiber are higher than copper because of the skill needed for terminations. Overall, fiber is more expensive than copper in the short run, but it may actually be less expensive in the long run. Fiber typically costs less to maintain, has much less downtime, and requires less networking hardware. And fiber eliminates the need to recable for higher network performance.


Multimode or single-mode, duplex or simplex?

Multimode-Multimode fiber optic cable can be used for most general fiber applications. Use multimode fiber for bringing fiber to the desktop, for adding segments to your existing network, or in smaller applications such as alarm systems. Multimode cable comes with two different core sizes: 50 micron or 62.5 micron.


Single-mode-Single-mode is used over distances longer than a few miles. Telcos use it for connections between switching offices. Single-mode cable features an 8.5-micron glass core.


Duplex-Use duplex multimode or single-mode fiber optic cable for applications that require simultaneous, bidirectional data transfer. Workstations, fiber switches and servers, fiber modems, and similar hardware require duplex cable. Duplex is available in single- and multimode.


Simplex-Because simplex fiber optic cable consists of only one fiber link, you should use it for applications that only require one-way data transfer. For instance, an interstate trucking scale that sends the weight of the truck to a monitoring station or an oil line monitor that sends data about oil flow to a central location. Simplex fiber comes in single- and multimode types.


50- vs. 62.5-micron cable.

Although 50-micron fiber cable features a smaller core, which is the light-carrying portion of the fiber, both 62.5- and 50-micron cable feature the same glass cladding diameter of 125 microns. You can use both in the same types of networks, although 50-micron cable is recommended for premise applications: backbone, horizontal, and intrabuilding connections, and should be considered especially for any new construction and installations. And both can use either LED or laser light sources.


The big difference between 50-micron and 62.5-micron cable is in bandwidth-50-micron cable features three times the bandwidth of standard 62.5-micron cable, particularly at 850 nm. The 850-nm wavelength is becoming more important as lasers are being used more frequently as a light source.


Other differences are distance and speed. 50-micron cable provides longer link lengths and/or higher speeds in the 850-nm wavelength. See the table below.




The ferrules: ceramic or composite?

As a general rule, use ceramic ferrules for critical network connections such as backbone cables or for connections that will be changed frequently, like those in wiring closets. Ceramic ferrules are more precisely molded and fit closer to the fiber, which gives the fiber optic cables a lower optical loss.


Use composite ferrules for connections that are less critical to the network’s overall operation and less frequently changed. Like their ceramic counterparts, composite ferrules are characterized by low loss, good quality, and a long life. However, they are not as precisely molded and slightly easier to damage, so they aren’t as well-suited for critical connections.


Testing and certifying fiber optic cable.

If you’re accustomed to certifying copper cable, you’ll be pleasantly surprised at how easy it is to certify fiber optic cable because it’s immune to electrical interference. You only need to check a few measurements.

Attenuation (or decibel loss)-Measured in decibels/kilometer (dB/km), this is the decrease of signal strength as it travels through the fiber cable. Generally, attenuation problems are more common on multimode fiber optic cables.

Return loss-This is the amount of light reflected from the far end of the cable back to the source. The lower the number, the better. For example, a reading of -60 decibels is better than -20 decibels. Like attenuation, return loss is usually greater with multimode cable.

Graded refractive index-This measures how the light is sent down the fiber. This is commonly measured at wavelengths of 850 and 1300 nanometers. Compared to other operating frequencies, these two ranges yield the lowest intrinsic power loss. (NOTE: This is valid for multimode fiber only.)

Propagation delay-This is the time it takes a signal to travel from one point to another over a transmission channel.

Optical time-domain reflectometry (OTDR)-This enables you to isolate cable faults by transmitting high-frequency pulses onto a cable and examining their reflections along the cable. With OTDR, you can also determine the length of a fiber optic cable because the OTDR value includes the distance the optic signal travels.


There are many fiber optic testers on the market today. Basic fiber optic testers function by shining a light down one end of the cable. At the other end, there’s a receiver calibrated to the strength of the light source. With this test, you can measure how much light is going to the other end of the cable. Generally, these testers give you the results in dB lost, which you then compare to the loss budget. If the measured loss is less than the number calculated by your loss budget, your installation is good.


Newer fiber optic testers have a broad range of capabilities. They can test both 850- and 1300-nanometer signals at the same time and can even check your cable for compliance with specific standards.


Fiber precautions.

A few properties particular to fiber optic cable can cause problems if you aren’t careful during installation.

Intrinsic power loss-As the optic signal travels through the fiber core, the signal inevitably loses some speed through absorption, reflection, and scattering. This problem is easy to manage by making sure your splices are good and your connections are clean.

Microbending-Microbends are minute deviations in fiber caused by excessive bends, pinches, and kinks. Using cable with reinforcing fibers and other special manufacturing techniques minimizes this problem.

Connector loss-Connector loss occurs when two fiber segments are misaligned. This problem is commonly caused by poor splicing. Scratches and dirt introduced during the splicing process can also cause connector loss.

Coupling loss-Similar to connector loss, coupling loss results in reduced signal power and is from poorly terminated connector couplings.


Remember to be careful and use common sense when installing fiber cable. Use clean components. Keep dirt and dust to a minimum. Don’t pull the cable excessively or bend it too sharply around any corners. That way, your fiber optic installation can serve you well for many years.

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Black Box Explains...NEMA ratings for enclosures.

The National Electrical Manufacturers’ Association (NEMA) issues guidelines and ratings for an enclosure’s level of protection against contaminants that might come in contact with its enclosed equipment.

There are many numerical... more/see it nowNEMA designations; we’ll discuss NEMA enclosures relevant to our on-line catalog: NEMA 3, NEMA 3R, NEMA 4, NEMA 4X, and NEMA 12.

NEMA 3 enclosures, designed for both indoor and outdoor use, provide protection against falling dirt, windblown dust, rain, sleet, and snow, as well as ice formation.

The NEMA 3R rating is identical to NEMA 3 except that it doesn’t specify protection against windblown dust.

NEMA 4 and 4X enclosures, also designed for indoor and outdoor use, protect against windblown dust and rain, splashing and hose-directed water, and ice formation. NEMA 4X goes further than NEMA 4, specifying that the enclosure will also protect against corrosion caused by the elements.

NEMA 12 enclosures are constructed for indoor use only and are designed to provide protection against falling dirt, circulating dust, lint, fibers, and dripping or splashing noncorrosive liquids. Protection against oil and coolant seepage is also a prerequisite for NEMA 12 designation. collapse


Black Box Explains…Liquid cooling.

The trend toward high-density installations with higher-powered CPUs has made heat a critical issue in data centers. Blade servers present a special challenge—a rack of blade servers can dissipate more... more/see it nowthan 25 kW, generating more heat than an electric oven.

Heat-generated problems
The heat generated in today’s high-density data centers can shorten equipment lifespan, negatively affect equipment performance, and cause downtime. Traditional air-cooling methods such as hot/cold aisle arrangements simply can’t keep up with these heat-generating installations. Data center managers often try to compensate for the inefficiency of air cooling by under-populating racks, but this wastes space—an often scarce commodity in modern data centers.

Why liquid
Because of the inherent inefficiencies of air cooling, many data centers have turned to liquid cooling through water or other refrigerants. Liquids have far greater heat transfer properties than air—water is 3400 times more efficient than air—and can cool far greater equipment densities.

Liquid cooling is usually done at the rack level using the airflow from the servers to move the heat to a cooling unit where it’s removed by liquid, neutralizing heat at the source before it enters the room. Liquid cooling may also be done at the component level, where cooling liquid is delivered directly to individual components. Liquid cooling may also arrive in the form of portable units for cooling hot spots.

Liquid cooling options
Types of liquid cooling commonly used in data centers include:

  • Cabinet-door liquid cooling: With this method, cooling units are special cabinet doors that contain sealed tubes filled with chilled liquid. The liquid is circulated through the door to remove heat vented by equipment fans. Because liquid-cooled doors can replace standard cabinet doors, they’re the favored method for retrofitting liquid cooling into existing data centers.
  • Integrated liquid cooling: This consists of a specialized sealed cabinet that has channels for liquid cooling built into it to act as heat exchangers. Fans move hot air past the heat exchangers before sending the cooled air back to the servers. These cabinets are closed systems that release very little heat into the room.
  • Component-based liquid cooling: Some servers are preconfigured with integrated liquid-based cooling modules. After the servers are installed, liquid is circulated through the cooling modules.
  • Immersion cooling: This rather counterintuitive cooling method immerses servers in a non-conductive liquid, which is circulated to cool the servers.
  • Portable liquid cooling: These are small units that operate by blowing air across water-cooled coils. They can usually accept water from any source—including a nearby faucet. They’re generally plumbed with ordinary garden hoses and require no special skills to use. Portable cooling units are intended for emergency cooling rather than as a permanent solution.


Liquid cooling requires a shift in the way you think about cooling. Installation may require that you acquire a new skill set or hire a professional installer. However, the space savings and cost savings gained through liquid cooling more than make up for the inconvenience of installing a new cooling technology.

Not only does liquid cooling enable data centers to operate at far greater densities than conventional air cooling does, it gets rid of the infrastructure associated with air cooling, enabling you to eliminate hot/cold aisles and raised floors. Liquid cooling can support from 25 to 80% more equipment in the same footprint, resulting in significantly lower infrastructure costs.

Add to this the fact that cooling is often the majority of a data center’s operating cost, and it’s plain to see why an investment in the efficiency of liquid cooling goes right to the bottom line. collapse


Black Box Explains...The fully accessorized rack.

After you choose your rack, consider how you’ll set it up and what accessories you might need.

Your rack may need to be secured. A typical rack has about a... more/see it now15"-deep base, providing some stability, but not enough to prevent the rack from tipping if heavy objects are mounted on it. To solve this problem, most rack bases can be bolted to the floor.

You also need to decide how to accommodate standalone equipment, which is not actually rackmounted or bolted to the rack. You can place small devices on a cantilevered shelf such as the RM001, however, you should place heavier items such as monitors on a center-weight shelf such as the RM377.

Small extras, such as Patch Panel Hinge Kits, can make your job easier. These hinges enable you to access the back of a patch panel simply by swinging it out from the rack. They’re particularly useful for racks in hard-to-reach areas.

If you need to mount both 19" and 23" equipment in the same rack, use a 23" rack with 23"-to-19" Rackmount Adapters to fit the 19" devices.

For a neater appearance, you can cover unused spaces in a rack with Filler Panels.

Cable management is also an important consideration. Our Horizontal and Vertical Cable Managers help you to route cables along the sides of racks, between racks, and to the rackmounted equipment. collapse


Black Box Explains...Dry contacts.

A dry contact, also called a volt-free contact, is a relay contact that does not supply voltage. The relay energizes or de-energizes when a change to its input has occurred.... more/see it nowIn other words, a dry contact simply detects whether or not an input switch is open or closed.

The dry contacts in the ServSensor Contact provide a simple two-wire interface that can be easily adapted to third-party sensors and devices. Because you define what the open or closed condition means, dry contacts are infinitely adaptable.

Use dry contacts to monitor alarms such as fire alarms, burglar alarms, and alarms on power systems such as UPSs. A very common use for dry contacts is to detect whether a cabinet door is open or closed. collapse


Black Box Explains...Rack units.

A Rack Unit is abbreviated as U. One Rack Unit (1U) is equal to 1.75" (4.44 cm).


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…Remote monitoring.

Beyond virus protection.
It has become almost automatic to protect your data center by backing up your servers, installing firewalls and virus protection, and keeping the protection up-to-date.

But what about... more/see it nowmore tangible threats? Do you have hot spots in your racks? If the cooling system shuts down, how will you know when temperatures climb out of control? Are you alerted to humidity changes or water leaks that threaten your equipment?

Planning for the unexpected is a critical task because there are more systems performing mission-critical functions than ever before. These systems are often deployed without the proper environmental infrastructure to support them. Equipment density is increasing constantly, which is creating more stress on ventilation and power.

The top three IT risks:
1. Environmental disruption.
The number one cause of downtime for remote locations, environmental problems go beyond fires and floods and affect as much as 30% of a company’s mission-critical infrastructure. Cooling and power are key points of exposure and increase as equipment density does.

2. Unnecessary risk.
When systems are housed in less-than-optimal settings, or are in remote and unsupervised locations, any error causes downtime. Yet, it’s not practical to have someone babysitting the servers.

3. Sabotage.
Regardless of the probability, terrorism is now something each of us must plan for. Your systems can also be brought down from within if the proper security safeguards are not in place.

What’s an environmental monitoring system?
Environmental monitoring products enable you to actively monitor the conditions in your rack, server room, data center, or anywhere else you need to protect critical assets. Conditions monitored include extreme temperatures, humidity, power spikes and surges, water leaks, smoke, and chemical materials. With proper environmental monitoring, you’re alerted to any conditions that could have an adverse effect on your mission-critical equipment. These products can also alert you to potential damage from human error, hacking, or prying fingers.

Environmental monitors consist of three main elements: a base unit, probes or sensors, and network connectivity and integration. The base units may contain one or more built-in sensors, as well as ports for hooking up external probes. Additionally, they include an Ethernet port and have software for remote configuration and graphing. This software may also work with existing network management software, such as SNMP systems.

Measurement.
An environmental monitoring appliance displays the values measured by the attached probes, e.g. temperature, humidity, airflow, status of dry contact, door, motion detector, and other sensors.

Data collecting and graphing.
Measurements are periodically stored in the internal memory or external storage media and displayed as graphs.

Alerting.
When the measured value exceeds the predefined threshold, it triggers an alert: a blinking LED on the front panel, an audible alarm, SNMP trap, e-mail, etc. The environmental monitoring appliance can also activate an external alarm system like a siren or strobe light.

Benefits of environmental monitoring:

  • Reduced downtime—When things go wrong, you’re the first to know. Minimize downtime by being alerted about conditions that cause damage to servers and other network devices.
  • Increased profits—Environmental monitoring systems are easy to implement. Also, they help you cut replacement equipment costs and redistribute your workforce more effectively.
  • Increased employee satisfaction—With built-in notification features like e-mail, SMS, and SNMP traps, a remote monitoring system enables employees to better manage their work.

  • Applications:
    Envornmental and security monitoring systems can be used for a variety of applications, including:
  • Data center monitoring
  • Computer room monitoring
  • Rackmount industrial equipment
  • Telecommunications
  • UPS/battery backup
  • Educational institutions
  • Food and beverage applications
  • Buildings/warehouses
  • Air conditioner/refrigerants/freezer monitoring
  • Greenhouses
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