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Black Box Explains...Selecting fiber line drivers.

When choosing a fiber driver, you should make a power budget, calculate the speed and distance of your cable run, and know the interface requirements of all your devices.

Many of... more/see it nowour fiber drivers are for single-mode fiber optic cable. Compared to multimode fiber, single-mode delivers up to 50 times more distance. And single-mode at full-duplex enables up to two times the data throughput of multimode fiber. collapse


Black Box Explains...Breakout-style cables.

With breakout- or fanout-style cables, the fibers are packaged individually. A breakout cable is basically several simplex cables bundled together in one jacket. Breakout cables are suitable for riser and... more/see it nowplenum applications, and conduit runs.

This differs from distribution-style cables where several tight-buffered fibers are bundled under the same jacket.

This design of the breakout cable adds strength to the cable, although that makes it larger and more expensive than distribution-style cables.

Because each fiber is individually reinforced, you can divide the cable into individual fiber lines. This enables quick connector termination, and eliminates the need for patch panels.

Breakout cable can also be more economical because it requires much less labor to terminate.

You may want to choose a cable that has more fibers than you actually need in case of breakage during termination or for future expansion. collapse


Black Box Explains... Buffers

A buffer (also called a spooler or a cache) is a temporary storage device used to share printers and compensate for a difference in speed and data flow between two... more/see it nowdevices. Buffers use RAM (Random-Access Memory) to take in data and hold it until the receiving device handles it.

A buffer serving a computer can be installed either internally or externally. Internal computer buffers are common in the forms of keyboard inputs, data caches, and video memory. An external buffer is usually used for printing.

An external buffer downloads jobs to the printer, freeing the computer so you can get back to work sooner.

A print buffer’s ports can be serial, parallel, or serial and parallel. Because a buffer’s ports operate independently of each other, a buffer also can be made to perform serial-to-parallel or parallel-to-serial conversion or to change the word structure and/or serial data rate (baud rate) of the data.

While most buffers are FIFO (First In, First Out), some advanced units can function as random-access buffers. For most serial buffers, hardware flow control is required, but some also support software (X-ON/X-OFF) control. Most buffers support printing of multiple copies of a document, provided the buffer has enough memory to store the entire print job. collapse


Black Box Explains...Multi-user ServSwitch products vs. multipoint access ServSwitch products.

A multi-user ServSwitch, such as the Matrix ServSwitch, enables two or more users to access different servers at the same time. So, for instance, one user can access “Server A”... more/see it nowwhile another user accesses “Server B.” This is considered a “true two-channel” architecture because two users have independent access to CPUs. It should be pointed out that multiple users cannot access the same server at the same time.

A multipoint access ServSwitch, such as the ServSwitch Duo, provides two access points for control stations but requires that both users view the same server at the same time. So, if one user is accessing “Server A” on his screen, the other user is also seeing “Server A” on his screen. If the second user switches to “Server B,“ the first user will also switch to “Server B.” Only one of these users is actually in control. The user in control stays in control until his workstation is inactive for a period of time (selectable). Then the other station can take control.

A multipoint access ServSwitch is useful when simultaneous, independent access is not required—just the ability to access CPUs from more than one place.

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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... Basic Printer Switches

Mechanical—A mechanical switch is operated by a knob or by push buttons and uses a set of copper or gold-plated copper contacts to make a connection. The internal resistance created... more/see it nowby this type of connection will affect your signal’s transmission distance and must be taken into account when calculating cable lengths.

Electronic—Although electronic switches are controlled by knobs and pushbuttons like mechanical switches, the switching is accomplished with electronic gates not mechanical contacts. Electronic switches don’t have the internal resistance of a mechanical switch—some even have the ability to drive signals for longer distances. And since they don’t generate electronic spikes like mechanical switches, they’re safe for sensitive components such as HP® laser printers. Some electronic switches can be operated remotely. collapse


Black Box Explains... SNMP.

SNMP (Simple Network Management Protocol) management is the standard for LAN management, particularly in mission-critical applications. The standard is controlled by the Internet Engineering Task Force (IETF). It was designed... more/see it nowto manage network configuration, performance, faults, accounting, and security.

An SNMP agent must be present at the device level (a router or a hub, for example), either built into the unit or as a proxy agent, and is accessed through a remote terminal. SNMP does not follow a polling protocol. It waits to receive data from the remote device or sends data based on operator commands.

By using one common set of standards, SNMP enables network administrators to manage, monitor, and control their SNMP-compliant network equipment with one management system and from one management station. If a network device goes down, it|s possible to both pinpoint and troubleshoot the problem more efficiently. And a network administrator isn’t limited to equipment from just one vendor when using an SNMP program. collapse


Black Box Explains...FDDI

Fiber Distributed Data Interface (FDDI) is a networking standard for operating at speeds of up to 100 Mbps. The standard FDDI network is set up in a ring topology with... more/see it nowtwo rings that transmit signals in opposite directions to a series of nodes. FDDI accommodates up to 500 nodes per dual-ring network with spacing up to 2 kilometers between adjacent nodes. FDDI uses the same token-passing scheme as the IEEE 802.5 Token Ring network to control transmission around the loop. collapse


Black Box Explains...Fiber optic ferrule sleeves.

In a fiber optic adapter, the internal ferrule sleeve holds the fiber in place and aligns the filament of one fiber ferrule with its mate. The ferrule sleeve is the... more/see it nowmost expensive component to manufacture in a fiber optic adapter, accounting for approximately 80% of the total adapter cost.

The ferrule alignment sleeves are also the most critical part of a fiber optic connection process. They provide the bridge between one cable’s ferrule and another cable’s ferrule interface. The precision of the ferrule sleeve and its hole determines how well the fibers align, which affects the light signal transmission.

Fiber optic adapters are generally made with ceramic or metal ferrule sleeves. Some adapters also feature ferrule sleeves that are a combination of these materials.

Ceramic ferrule sleeves are more precisely molded and fit close to the fiber ferrule. This precise molding gives the fiber optic connection a lower optical loss. As a general rule, use ceramic ferrule sleeves for critical network connections, such as backbone runs in highly secure networks or for connections that will be changed frequently, like those in wiring closets. Ceramic ferrule sleeves best suit single-mode cable connections.

Ferrule sleeves made of metal, such as bronze ferrules, offer more durability than ceramic sleeves, but they may not offer the same precision alignment as ceramic ferrule sleeves. Drilling an accurate hole through the metal ferrule sleeve can be difficult, and that can result in less accurate fiber alignment. The use of watch-jeweled centering improves alignment. But overall, metal ferrule sleeves are better suited for multimode fiber applications where absolute alignment isn’t crucial.
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Black Box Explains... Printer Sharing with Windows

Unlike the earlier DOS operating systems, Windows® doesn’t check to see if the printer is busy at the very beginning of the printing process. Windows will send out data to... more/see it nowstart a job even if the printer is signaling busy or unavailable. If your print sharer doesn’t have a buffer, critical printer-initialization information can be lost before your job is started. Once the initialization information is lost, the printer cannot interpret the job correctly.

A buffered print-sharing device is the most practical solution. When Windows starts printing to a buffered port, it “thinks“ it’s talking directly to the printer, and the critical initialization information is stored by the buffer. The buffer can send out a busy signal to Windows, so it delays sending more information until the buffer is accessible again. collapse

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