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Black Box Explains... G.703.

G.703 is the ITU-T recommendation covering the 4-wire physical interface and digital signaling specification for transmission at 2.048 Mbps (E1). G.703 also includes specifications for U.S. 1.544-Mbps T1 but is... more/see it nowstill generally used to refer to the European 2.048-Mbps transmission interface. 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...DIN rail.

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...How fiber is insulated for use in harsh environments.

Fiber optic cable not only gives you immunity to interference and greater signal security, but it’s also constructed to insulate the fiber’s core from the stress associated with use in... more/see it nowharsh environments.

The core is a very delicate channel that’s used to transport data signals from an optical transmitter to an optical receiver. To help reinforce the core, absorb shock, and provide extra protection against cable bends, fiber cable contains a coating of acrylate plastic.

In an environment free from the stress of external forces such as temperature, bends, and splices, fiber optic cable can transmit light pulses with minimal attenuation. And although there will always be some attenuation from external forces and other conditions, there are two methods of cable construction to help isolate the core: loose-tube and tight-buffer construction.

In a loose-tube construction, the fiber core literally floats within a plastic gel-filled sleeve. Surrounded by this protective layer, the core is insulated from temperature extremes, as well as from damaging external forces such as cutting and crushing.

In a tight-core construction, the plastic extrusion method is used to apply a protective coating directly over the fiber coating. This helps the cable withstand even greater crushing forces. But while the tight-buffer design offers greater protection from core breakage, it’s more susceptible to stress from temperature variations. Conversely, while it’s more flexible than loose-tube cable, the tight-buffer design offers less protection from sharp bends or twists. collapse


Black Box Explains…Before the ServSwitch.

Before the introduction of the ServSwitch, accessing more than one CPU from a single keyboard, monitor, and mouse was problematic. Keyboard/video (KV) or keyboard/video/mouse (KVM) switches frequently caused CPUs to... more/see it nowlock up because the CPUs weren’t always receiving the signals they expected from the keyboard. Managing server farms was a nuisance because either each server needed its own keyboard, monitor, and mouse, it or was subject to frequent rebooting if used with a KVM switch.

The BLACK BOX® ServSwitch™ KVM Switch changed all that. The ServSwitch enables frequent switching between multiple CPUs (up to 3000!) without the danger of CPUs locking up. That’s because the ServSwitch is built with sophisticated circuitry that keeps feeding each CPU the keyboard and mouse signals it expects.

So why are we still selling preServSwitch keyboard/video switches? The Number 1 reason is many of our customers have preinstalled applications in which these switches are specified, so we keep stocking them as a service. Another reason is there is still some call for these switches for applications in which only limited switching is required.

However, for most KVM applications, we recommend a BLACK BOX® ServSwitch™ KVM Switch as the most reliable switching solution. We have ServSwitch products and accessories for everything from a simple desktop application to managing all the servers in your enterprise network.

Simplify and save with BLACK BOX® ServSwitch™ Technology! collapse


Black Box Explains...RS-232.

RS-232, also known as RS-232C and TIA/EIA-232-E, is a group of electrical, functional, and mechanical specifications for serial interfaces between computers, terminals, and peripherals. The RS-232 standard was developed by... more/see it nowthe Electrical Industries Association (EIA), and defines requirements for connecting data communications equipment (DCE)—modems, converters, etc.—and data terminal equipment (DTE)—computers, controllers, etc.) devices. RS-232 transmits data at speeds up to 115 Kbps and over distances up to 50 feet (15.2 m).

The standard, which is functionally equivalent to ITU V.24/V.28, specifies the workings of the interface, circuitry, and connector pinning. Both sync and async binary data transmission fall under RS-232. Although RS-232 is sometimes still used to transmit data from PCs to peripheral devices, the most common uses today are for network console ports and for industrial devices.

Even though RS-232 is a “standard,” you can’t necessarily expect seamless communication between two RS-232 devices. Why? Because different devices have different circuitry or pinning, and different wires may be designated to perform different functions.

The typical RS-232 connector is DB25, but some PCs and other data communication devices have DB9 connectors and many newer devices have RJ-45 RS-232 ports. To connect 9-pin PC ports or RJ-45 to devices with 25-pin connectors, you will require a simple adapter cable. collapse


Black Box Explains...T1 and E1 benefits.

If you manage a heavy-traffic data network and you demand high bandwidth for high speeds, Black Box has what you need to send your data digitally over super-fast T1 or... more/see it nowE1 communication lines.

Both T1 and E1 are foundations of global voice communication.
Developed more than 30 years ago and commercially available since 1983, T1 and E1 go virtually anywhere phone lines go, but faster. T1 sends data up to 1.544 Mbps. E1 supports speeds to 2.048 Mbps. No matter where you need to connect—North, South, or Central America, Europe, or the Pacific Rim—T1 and E1 can get your data there—fast!

Both services provide flexibility for a multitude of applications. Whether you need to drive a private, point-to-point line or a high- speed circuit, provide corporate access to the Internet or inbound access to your own webserver, or support a voice/data/fax/video WAN that extends halfway around the world, T1 or E1 can make the connection.

Both offer cost-effective connections.
In recent years, competition among telco service providers has led to increasingly more affordable prices for T1 and E1 services. In fact, most companies seriously considering a shift to T1 or E1 will find they can negotiate even better rates with just a little comparative cost analysis.

Some typical applications include:
• Accessing public Frame-Relay networks or public switched telephone networks for voice and fax.
• Merging voice and data traffic. A single T1 or E1 line can give you several additional voice and data lines at no additional cost.
• Making LAN connections. If you’re linking LANs, a T1 or E1 line offers excellent performance.
• Sending bandwidth-intensive data such as CAD/CAM, MRI, CAT-scan images, and other graphics with large files. collapse


Black Box Explains...Gigabit Ethernet.

As workstations and servers migrated from ordinary 10-Mbps Ethernet to 100-Mbps speeds, it became clear that even greater speeds were needed. Gigabit Ethernet was developed for an even faster Ethernet... more/see it nowstandard to handle the network traffic generated on the server and backbone level by Fast Ethernet. Gigabit Ethernet delivers an incredible 1000 Mbps (or 1 Gbps), 100 times faster than 10BASE-T. At that speed, Gigabit Ethernet can handle even the traffic generated by campus network backbones. Plus it provides a smooth upgrade path from 10-Mbps Ethernet and 100-Mbps Fast Ethernet at a reasonable cost.

Compatibility
Gigabit Ethernet is a true Ethernet standard. Because it uses the same frame formats and flow control as earlier Ethernet versions, networks readily recognize it, and it’s compatible with older Ethernet standards. Other high-speed technologies (ATM, for instance) present compatibility problems such as different frame formats or different hardware requirements.

The primary difference between Gigabit Ethernet and earlier implementations of Ethernet is that Gigabit Ethernet almost always runs in full-duplex mode, rather than the half-duplex mode commonly found in 10- and 100-Mbps Ethernet.

One significant feature of Gigabit Ethernet is the improvement to the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) function. In half-duplex mode, all Ethernet speeds use the CSMA/CD access method to resolve contention for shared media. For Gigabit Ethernet, CSMA/CD has been enhanced to maintain the 200-meter (656.1-ft.) collision diameter.

Affordability and adaptability
You can incorporate Gigabit Ethernet into any standard Ethernet network at a reasonable cost without having to invest in additional training, cabling, management tools, or end stations. Because Gigabit Ethernet blends so well with your other Ethernet applications, you have the flexibility to give each Ethernet segment exactly as much speed as it needs—and if your needs change, Ethernet is easily adaptable to new network requirements.

Gigabit Ethernet is the ideal high-speed technology to use between 10-/100-Mbps Ethernet switches or for connection to high-speed servers with the assurance of total compatibility with your Ethernet network.

When Gigabit Ethernet first appeared, fiber was crucial to running Gigabit Ethernet effectively. Since then, the IEEE802.3ab standard for Gigabit over Category 5 cable has been approved, enabling short stretches of Gigabit speed over existing copper cable. Today, you have many choices when implementing Gigabit Ethernet:

1000BASE-X
1000BASE-X refers collectively to the IEEE802.3z standards: 1000BASE-SX, 1000BASE-LX, and 1000BASE-CX.

1000BASE-SX
The “S“ in 1000BASE-SX stands for “short.“ It uses short wavelength lasers, operating in the 770- to 860-nanometer range, to transmit data over multimode fiber. It’s less expensive than 1000BASE-LX, but has a much shorter range of 220 meters over typical 62.5-µm multimode cable.

1000BASE-LX
The “L“ stands for “long.“ It uses long wavelength lasers operating in the wavelength range of 1270 to 1355 nanometers to transmit data over single-mode fiber optic cable. 1000BASE-LX supports up to 550 meters over multimode fiber or up to 10 kilometers over single-mode fiber.

1000BASE-CX
The “C“ stands for “copper.“ It operates over special twinax cable at distances of up to 25 meters. This standard never really caught on.

Gigabit over CAT5—1000BASE-TX
The 802.3ab specification, or 1000BASE-TX, enables you to run IEEE-compliant Gigabit Ethernet over copper twisted-pair cable at distances of up to 100 meters of CAT5 or higher cable.

Gigabit Ethernet uses all four twisted pairs within the cable, unlike 10BASE-T and 100BASE-TX, which only use two of the four pairs. It works by transmitting 250 Mbps over each of the four pairs in 4-pair cable. collapse


Black Box Explains... Manual switch chassis styles.

There are five manual switch chassis styles: three for standalone switches (Styles A, B, and C) and two for rackmount switches (Styles D and E). Below are the specifications for... more/see it noweach style.

Standalone Switches

Chassis Style A
Size — 2.5"H x 6"W x 6.3"D (6.4 x 15.2 x 16 cm
Weight — 1.5 lb. (0.7 kg)
Chassis Style B
Size — 3.5"H x 6"W x 6.3"D (8.9 x 15.2 x 16 cm)
Weight — 1.5 lb. (0.7 kg)
Chassis Style C
Size — 3.5"H x 17"W x 5.9"D (8.9 x 43.2 x 15 cm)
Weight — 8.4 lb. (3.8 kg)

Rackmount Switches

Chassis Style D (Mini Chassis)
Size — 3.5"H x 19"W x 5.9"D (8.9 x 48.3 x 15 cm)
Chassis Style E (Standard Chassis)
Size — 7"H x 19"W x 5.9"D (17.8 x 48.3 x 15 cm) collapse


Black Box Explains...Optical isolation and ground loops.

Optical isolation protects your equipment from dangerous ground loops. A ground loop is a current across a conductor, created by a difference in potential between two grounded points, as in... more/see it nowequipment in two buildings connected by a run of RS-232 or other data line. When two devices are connected and their potentials are different, voltage flows from high to low by traveling through the data cable. If the voltage potential is large enough, your equipment won’t be able to handle the excess voltage and one of your ports will be damaged.

Ground loops can also exist in industrial environments. They can be created when power is supplied to your equipment from different transformers or when someone simply turns equipment on and off. Ground loops can also occur when there is a nearby lightning strike. During an electrical storm, the ground at one location can be charged differently than the other location, causing a heavy current flow through the serial communication lines that damage components.

You can’t test for ground loops. You don’t know you have one until a vital component fails. Only prevention works. For data communication involving copper cable, optical isolation is key.

With optical isolation, electrical data is converted to an optical beam, then back to an electrical pulse. Because there is no electrical connection between the DTE and DCE sides, an optical isolator— unlike a surge suppressor—will not pass large sustained power surges through to your equipment. Since data only passes through the optical isolator, your equipment is protected against ground loops and other power surges. collapse

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