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The ANSI/ISA Standard and Hazardous Locations

Fires and explosions are a major safety concern in industrial plants. Electrical equipment that must be installed in these locations should be specifically designed and tested to operate under extreme... more/see it nowconditions. The hazardous location classification system was designed to promote the safe use of electrical equipment in those areas “where fire or explosion hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust, or ignitable fibers of flyings.”

The NEC and CSA define hazardous locations by three classes:
Class 1: Gas or vapor hazards
Class 2: Dust hazards
Class 3: Fibers and flyings

Two divisions:
Division 1: An environment where ignitable gases, liquids, vapors or dusts can exist Division 2: Locations where ignitables are not likely to exist

Hazardous classes are further defined by groups A, B, C, D, E, F, and G:
A. Acetylene
B. Hydrogen
C. Ethlene, carbon monoxide
D. Hydrocarbons, fuels, solvents
E. Metals
F. Carbonaceous dusts including coal, carbon black, coke
G. Flour, starch, grain, combustible plastic or chemical dust

ANSI/ISA 12.12.01
Our line of Industrial Ethernet Switches (LEH1208A, LEH1208A-2GMMSC, LEH1216A and LEH1216A-2GMMSC) is fully compliant with ANSI/ISA 12.12.01, a construction standard for Nonincendive Electrical Equipment for Use in Class I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous (Classified) Locations. ANSI/ISA 12.12.01-2000 is similar to UL1604, but is more stringent (for a full list of changes, see Compliance Today). UL1604 was withdrawn in 2012 and replaced with ISA 12.12.01.

The standard provides the requirements for the design, construction, and marking of electrical equipment or parts of such equipment used in Class I and Class II, Division 2 and Class III, Divisions 1 and 2 hazardous (classified) locations. This type of equipment, in normal operation, is not capable of causing ignition.

The standard establishes uniformity in test methods for determining the suitability of equipment as related to their potential to ignite to a specific flammable gas or vapor-in-air mixture, combustible dust, easily ignitable fibers, or flyings under the following ambient conditions:
a) an ambient temperature of -25°C to 40°C.
b) an oxygen concentration of not greater than 21 percent by volume.
c) a pressure of 80 kPa (0.8 bar) to 110 kPa (1.1 bar).

The standard is available for purchase at www.webstore.ansi.org. To learn more about ANSI/ISA 12.12.01 and hazardous location types, visit https://www.osha.gov/doc/outreachtraining/htmlfiles/hazloc.html. -- collapse


Black Box Explains...Why media converters need SNMP.

The number of Ethernet switches and fiber optic segments being added to Ethernet networks keeps increasing. And as long as most Ethernet switches are only available with 10BASE-T and 100BASE-TX... more/see it nowinterfaces, media converters will remain in demand.

Until now, a failure on the network could go unnoticed. Once a failure was detected, it could take a long time to isolate it, especially if a technician had to be sent to the site. But media converters with SNMP eliminate some of the guesswork.

With SNMP, the IS manager can detect a failure, isolate it to a specific port, and determine what hardware is required to repair it. A technician can then be sent directly to the right place to fix faulty hardware or repair a broken cable.

SNMP enables you to set up alarms or traps when a link is down. You can turn features on and off from a central terminal, so there’s no need to leave your desk. You can also monitor power supplies and replace them without interrupting service. SNMP management reduces the time and money it takes to get your network up and running again. The users on your network will notice—and appreciate—the improved service and reliability. collapse


Black Box Explains...vDSL.

VDSL (Very High Bit-Rate Digital Subscriber Line or Very High-Speed Digital Subscriber Line) is a “last-mile” broadband solution for both businesses and homes, providing economical, high-speed connections to fiber optic... more/see it nowbackbones.

VDSL enables the simultaneous transmission of voice, data, and video on existing voice-grade copper wires. Depending on the intended applications, you can set VDSL to run symmetrically or asymmetrically. VDSL’s high bandwidth allows for applications such as high-definition television, video-on-demand (VOD), high-quality videoconferencing, medical imaging, fast Internet access, and regular voice telephone services—all over a single voice-grade twisted pair. The actual VDSL distances you achieve vary based on line rate, gauge and type of wire, and noise/crosstalk environment. collapse


Black Box Explains...UARTs at a glance.

Universal Asynchronous Receiver/Transmitters (UARTs) are integrated circuits that convert bytes from the computer bus into serial bits for transmission. By providing surplus memory in a buffer, UARTs help applications overcome... more/see it nowthe factors that can hinder system performance, providing maximum throughput to high-performance peripherals without slowing down CPUs.

Early UARTs such as 8250 and 16450 did not include buffering (RAM or memory). With the advent of higher-speed devices, the need for UARTs that could handle more data became critical. The first buffered UART was the 16550, which incorporates a 16-byte First In First Out (FIFO) buffer and provides greater throughput than its predecessors.

Manufacturers have been developing enhanced UARTs that continue to increase performance standards. These faster chips provide improvements such as larger buffers and increased speeds. Here are the rates of today’s common UARTs:

UART FIFO Buffer Rate Supported
16550 16-byte 115.2 kbps
16554 16-byte 115.2 kbps
16650 32-byte 460.8 kbps (burst rate)
16654 64-byte 460.8 kbps (burst rate)
16750 64-byte 460.8 kbps (burst rate)
16850 128-byte 460.8 kbps (sustained rate)
16854 128-byte 460.8 kbps (sustained rate) 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...How computer speeds are enhanced with PCI buses and UARTs.

The Peripheral Component Interconnect (PCI®) Bus enhances both speed and throughput. The 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.

UARTs (Universal Asynchronous Receiver/ Transmitters) are integrated circuits that convert bytes from the computer bus into serial bits for transmission. By providing surplus memory in a buffer, UARTs help your applications overcome the factors that slow down your system. collapse


Black Box Explains...Single-strand fiber WDM.

Traditional fiber optic media converters perform a useful function but don’t really reduce the amount of cable needed to send data on a fiber segment. They still require two strands... more/see it nowof glass to send transmit and receive signals for fiber media communications. Wouldn’t it be better to combine these two logical communication paths within one strand?

That’s exactly what single-strand fiber conversion does. It compresses the transmit and receive wavelengths into one single-mode fiber strand.

The conversion is done with Wave-Division Multiplexing (WDM) technology. WDM technology increases the information-carrying capacity of optical fiber by transmitting two signals simultaneously at different wavelengths on the same fiber. The way it usually works is that one unit transmits at 1310 nm and receives at 1550 nm. The other unit transmits at 1550 nm and receives at 1310 nm. The two wavelengths operate independently and don’t interfere with each other. This bidirectional traffic flow effectively converts a single fiber into a pair of “virtual fibers,” each driven independently at different wavelengths.

Although most implementations of WDM on single-strand fiber offer two channels, four-channel versions are just being introduced, and versions offering as many as 10 channels with Gigabit capacity are on the horizon.

WDM on single-strand fiber is most often used for point-to-point links on a long-distance network. It’s also used to increase network capacity or relieve network congestion. collapse


Black Box Explains...Power problems.

Sags
The Threat — A sag is a decline in the voltage level. Also known as “brownouts,” sags are the most common power problem.

The Cause — Sags can be caused... more/see it nowlocally by the start-up demands of electrical devices such as motors, compressors, and elevators. Sags may also happen during periods of high electrical use, such as during a heat wave.

The Effect — Sags are often the cause of “unexplained” computer glitches such as system crashes, frozen keyboards, and data loss. Sags can also reduce the efficiency and lifespan of electrical motors.

Blackouts
The Threat — A blackout is a total loss of power.

The Cause — Blackouts are caused by excessive demand on the power grid, an act of nature such as lightning or an earthquake, or a human accident such as a car hitting a power pole or a backhoe digging in the wrong place.

The Effect — Of course a blackout brings everything to a complete stop. You also lose any unsaved data stored in RAM and may even lose the total contents of your hard drive.

Spikes
The Threat — A spike, also called an impulse, is an instantaneous, dramatic increase in voltage.

The Cause — A spike is usually caused by a nearby lightning strike but may also occur when power is restored after a blackout.

The Effect — A spike can damage or completely destroy electrical components and also cause data loss.

Surges
The Threat — A surge is an increase in voltage lasting at least 1/120 of a second.

The Cause — When high-powered equipment such as an air conditioner is powered off, the excess voltage is dissipated though the power line causing a surge.

The Effect — Surges stress delicate electronic components causing them to wear out before their time.

Noise
The Threat — Electrical noise, more technically called electromagnetic interference (EMI) and radio frequency interference (RFI), interrupts the smooth sine wave expected from electrical power.

The Cause — Noise has many causes including nearby lightning, load switching, industrial equipment, and radio transmitters. It may be intermittent or chronic.

The Effect — Noise introduces errors into programs and data files. collapse


SHDSL, VDSL, VDSL2, ADSL, and SDSL.

xDSL, a term that encompasses the broad range of digital subscriber line (DSL) services, offers a low-cost, high-speed data transport option for both individuals and businesses, particularly in areas without... more/see it nowaccess to cable Internet.

xDSL provides data transmission over copper lines, using the local loop, the existing outside-plant telephone cable network that runs right to your home or office. DSL technology is relatively cheap and reliable.

SHDSL can be used effectively in enterprise LAN applications. When interconnecting sites on a corporate campus, buildings and network devices often lie beyond the reach of a standard Ethernet segment. Now you can use existing copper network infrastructure to connect remote LANS across longer distances and at higher speeds than previously thought possible.

There are various forms of DSL technologies, all of which face distance issues. The quality of the signals goes down with increasing distance. The most common will be examined here, including SHDSL, ADSL, and SDSL.

SHDSL (also known as G.SHDSL) (Single-Pair, High-Speed Digital Subscriber Line) transmits data at much higher speeds than older versions of DSL. It enables faster transmission and connections to the Internet over regular copper telephone lines than traditional voice modems can provide. Support of symmetrical data rates makes SHDSL a popular choice for businesses for PBXs, private networks, web hosting, and other services.

Ratified as a standard in 2001, SHDSL combines ADSL and SDSL features for communications over two or four (multiplexed) copper wires. SHDSL provides symmetrical upstream and downstream transmission with rates ranging from 192 kbps to 2.3 Mbps. As a departure from older DSL services designed to provide higher downstream speeds, SHDSL specified higher upstream rates, too. Higher transmission rates of 384 kbps to 4.6 Mbps can be achieved using two to four copper pairs. The distance varies according to the loop rate and noise conditions.

For higher-bandwidth symmetric links, newer G.SHDSL devices for 4-wire applications support 10-Mbps rates at distances up to 1.3 miles (2 km). Equipment for 2-wire deployments can transmit up to 5.7 Mbps at the same distance.

SHDSL (G.SHDSL) is the first DSL standard to be developed from the ground up and to be approved by the International Telecommunication Union (ITU) as a standard for symmetrical digital subscriber lines. It incorporates features of other DSL technologies, such as ADSL and SDS, and is specified in the ITU recommendation G.991.2.

Also approved in 2001, VDSL (Very High Bitrate DSL) as a DSL service allows for downstream/upstream rates up to 52 Mbps/16 Mbps. Extenders for local networks boast 100-Mbps/60-Mbps speeds when communicating at distances up to 500 feet (152.4 m) over a single voice-grade twisted pair. As a broadband solution, VDSL enables the simultaneous transmission of voice, data, and video, including HDTV, video on demand, and high-quality videoconferencing. Depending on the application, you can set VDSL to run symmetrically or asymmetrically.

VDSL2 (Very High Bitrate DSL 2), standardized in 2006, provides a higher bandwidth (up to 30 MHz) and higher symmetrical speeds than VDSL, enabling its use for Triple Play services (data, video, voice) at longer distances. While VDSL2 supports upstream/downstream rates similar to VDSL, at longer distances, the speeds don’t fall off as much as those transmitted with ordinary VDSL equipment.

ADSL (Asymmetric DSL) provides transmission speeds ranging from downstream/upstream rates of 9 Mbps/640 kbps over a relatively short distance to 1.544 Mbps/16 kbps as far away as 18,000 feet. The former speeds are more suited to a business, the latter more to the computing needs of a residential customer.

More bandwidth is usually required for downstream transmissions, such as receiving data from a host computer or downloading multimedia files. ADSL’s asymmetrical nature provides more than sufficient bandwidth for these applications.

The lopsided nature of ADSL is what makes it most likely to be used for high-speed Internet access. And the various speed/distance options available within this range are one more point in ADSL’s favor. Like most DSL services standardized by ANSI as T1.413, ADSL enables you to lease and pay for only the bandwidth you need.

SDSL (Symmetric DSL) represents the two-wire version of HDSL—which is actually symmetric DSL, albeit a four-wire version. SDSL is also known within ANSI as HDSL2.

Essentially offering the same capabilities as HDSL, SDSL offers T1 rates (1.544 Mbps) at ranges up to 10,000 feet and is primarily designed for business applications.

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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

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