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Black Box Explains...UARTs and PCI buses.

Universal Asynchronous Receiver/Transmitters UARTs are designed to convert sync data from a PC bus to an async format that external I/O devices such as printers or modems use. UARTs insert... more/see it nowor remove start bits, stop bits, and parity bits in the data stream as needed by the attached PC or peripheral. They can provide maximum throughput to your high-performance peripherals without slowing down your CPU.

In the early years of PCs and single-application operating systems, UARTs interfaced directly between the CPU bus and external RS-232 I/O devices. Early UARTs did not contain any type of buffer because PCs only performed one task at a time and both PCs and peripherals were slow.

With the advent of faster PCs, higher-speed modems, and multitasking operating systems, buffering (RAM or memory) was added so that UARTs could handle more data. The first buffered UART was the 16550 UART, which incorporates a 16-byte FIFO (First In First Out) buffer and can support sustained data-transfer rates up to 115.2 kbps.

The 16650 UART features a 32-byte FIFO and can handle sustained baud rates of 460.8 kbps. Burst data rates of up to 921.6 kbps have even been achieved in laboratory tests.

The 16750 UART has a 64-byte FIFO. It also features sustained baud rates of 460.8 kbps but delivers better performance because of its larger buffer.

Used in newer PCI cards, the 16850 UART has a 128-byte FIFO buffer for each port. It features sustained baud rates of 460.8 kbps.

The Peripheral Component Interconnect (PCI®) Bus enhances both speed and throughput. PCI Local Bus is a high-performance bus that provides a processor-independent data path between the CPU and high-speed peripherals. PCI is a robust interconnect interface designed specifically to accommodate multiple high-performance peripherals for graphics, full-motion video, SCSI, and LANs.

A Universal PCI (uPCI) card has connectors that work with both a newer 3.3-V power supply and motherboard and with older 5.5-V versions. collapse

Black Box Explains...Category wiring standards

The ABCs of standards
There are two primary organizations dedicated to developing and setting structured cabling standards. In North America, standards are issued by the Telecommunications Industry Association (TIA),... more/see it nowwhich is accredited by the American National Standards Institute (ANSI). The TIA was formed in April 1988 after a merger with the Electronics Industry Association (EIA). That’s why its standards are commonly known as ANSI/TIA/EIA, TIA/EIA, or TIA.

Globally, the organizations that issue standards are the International Electrotechnical Commission (IEC) and the International Organization for Standardization (ISO). Standards are often listed as ISO/IEC. Other organizations include the Canadian Standards Association (CSA), CENELEC (European Committee for Electrotechnical Standardizations), and the Japanese Standards Association (JSA/JSI).

The committees of all these organizations work together and the performance requirements of the standards are very similar. But there is some confusion in terminology.

The TIA cabling components (cables, connecting hardware, and patch cords) are labeled with a ”category.” These components together form a permanent link or channel that is also called a ”category.” The ISO/IEC defines the link and channel requirements with a ”class” designation. But the components are called a ”category.”

The standards
Category 5 (CAT5) —ratified in 1991. It is no longer recognized for use in networking.

Category 5e (CAT5e), ISO/IEC 11801 Class D, ratified in 1999, is designed to support full-duplex, 4-pair transmission in 100-MHz applications. The CAT5e standard introduced the measurement for PS-NEXT, EL-FEXT, and PS-ELFEXT. CAT5e is no longer recognized for new installations. It is commonly used for 1-GbE installations.

Category 6 (CAT6) – Class E has a specified frequency of 250 MHz, significantly improved bandwidth capacity over CAT5e, and easily handles Gigabit Ethernet transmissions. CAT6 supports 1000BASE-T and, depending on the installation, 10GBASE-T (10-GbE).

10-GbE over CAT6 introduces Alien Crosstalk (ANEXT), the unwanted coupling of signals between adjacent pairs and cables. Because ANEXT in CAT6 10-GbE networks is so dependent on installation practices, TIA TSB-155-A and ISO/IEC 24750 qualifies 10-GbE over CAT6 over channels of 121 to 180 feet (37 to 55 meters) and requires it to be 100% tested, which is extremely time consuming. To mitigate ANEXT in CAT6, it is recommended that the cables be unbundled, that the space between cables be increased, and that non-adjacent patch panel ports be used. If CAT6 F/UTP cable is used, mitigation is not necessary and the length limits do not apply. CAT6 is not recommended for new 10-GbE installations.

Augmented Category 6 (CAT6A) –Class Ea was ratified in February 2008. This standard calls for 10-Gigabit Ethernet data transmission over a 4-pair copper cabling system up to 100 meters. CAT6A extends CAT6 electrical specifications from 250 MHz to 500 MHz. It introduces the ANEXT requirement. It also replaces the term Equal Level Far-End Crosstalk (ELFEXT) with Attenuation to Crosstalk Ratio, Far-End (ACRF) to mesh with ISO terminology. CAT6A provides improved insertion loss over CAT6. It is a good choice for noisy environments with lots of EMI. CAT6A is also well-suited for use with PoE+.

CAT6A UTP cable is significantly larger than CAT6 cable. It features larger conductors, usually 22 AWG, and is designed with more space between the pairs to minimize ANEXT. The outside diameter of CAT6A cable averages 0.29"–0.35" compared to 0.21"–0.24" for CAT6 cable. This reduces the number of cables you can fit in a conduit. At a 40% fill ratio, you can run three CAT6A cables in a 3/4" conduit vs. five CAT6 cables.

CAT6A UTP vs. F/UTP. Although shielded cable has the reputation of being bigger, bulkier, and more difficult to handle and install than unshielded cable, this is not the case with CAT6A F/UTP cable. It is actually easier to handle, requires less space to maintain proper bend radius, and uses smaller conduits, cable trays, and pathways. CAT6A UTP has a larger outside diameter than CAT6A F/UTP cable. This creates a great difference in the fill rate of cabling pathways. An increase in the outside diameter of 0.1", from 0.25" to 0.35" for example, represents a 21% increase in fill volume. In general, CAT6A F/UTP provides a minimum of 35% more fill capacity than CAT6A UTP. In addition, innovations in connector technology have made terminating CAT6A F/UTP actually easier than terminating bulkier CAT6A UTP.

Category 7 (CAT7) –Class F was published in 2002 by the ISO/IEC. It is not a TIA recognized standard and TIA plans to skip over it.

Category 7 specifies minimum performance standards for fully shielded cable (individually shielded pairs surrounded by an overall shield) transmitting data at rates up to 600 MHz. It comes with one of two connector styles: the standard RJ plug and a non-RJ-style plug and socket interface specified in IEC 61076-2-104:2.

Category 7a (CAT7a) –Class Fa (Amendment 1 and 2 to ISO/IEC 11801, 2nd Ed.) is a fully shielded cable that extends frequency from 600 MHz to 1000 MHz.

Category 8 – The TIA decided to skip Category 7 and 7A and go to Category 8. The TR-42.7 subcommittee is establishing specs for a 40-Gbps twisted-pair solution with a 2-GHz frequency. The proposed standard is for use in a two-point channel in a data center at 30 meters. It is expected to be ratified in February 2016. The TR-42.7 subcommittee is also incorporating ISO/IEC Class II cabling performance criteria into the standard. It is expected to be called TIA-568-C.2-1. The difference between Class I and Class II is that Class II allows for three different styles of connectors that are not compatible with one another or with the RJ-45 connector. Class I uses an RJ-45 connector and is backward compatible with components up to Category 6A. collapse

Black Box Explains...IRQs, COM Ports, and Windows

Windows® 95 normally requires each serial port to have its own unique Interrupt Request Line (IRQ). However, if you use a third-party communications driver that supports IRQ sharing, you can... more/see it nowshare interrupts. Unfortunately, data throughput will not be as high as with single interrupt port configurations.

With Windows NT®, you can share interrupts across multiple ports as long as the serial ports have an Interrupt Status Port (ISP) built into the card.

The Interrupt Service Routine, a software routine that services interrupts and requests processor time, reads the ISP and is immmediately directed to the port that has an interrupt pending. Compared to the polling method used if the serial ports don’t have an ISP, this feature can determine which port generated the interrupt up to four times more efficiently—and it almost eliminates the risk of lost data. Windows NT supports the ISP by enabling the user to configure the registry to match the card’s settings. Black Box models IC102C-R3, IC058C, and IC112C-R3 all have ISPs and come with a Windows NT setup utility to simplify installation and configuration.

If your serial port doesn’t have an ISP, the Interrupt Service Routine has to poll each port separately to determine which port generated the interrupt. collapse

Black Box Explains...Media converters.

Media converters interconnect different cable types such as twisted pair, fiber, and coax within an existing network. They are often used to connect newer Ethernet equipment to legacy cabling.... more/see it nowThey can also be used in pairs to insert a fiber segment into copper networks to increase cabling distances and enhance immunity to electromagnetic interference (EMI).

Traditional media converters are purely Layer 1 devices that only convert electrical signals and physical media. They don’t do anything to the data coming through the link so they’re totally transparent to data. These converters have two ports—one port for each media type. Layer 1 media converters only operate at one speed and cannot, for instance, support both 10-Mbps and 100-Mbps Ethernet.

Some media converters are more advanced Layer 2 Ethernet devices that, like traditional media converters, provide Layer 1 electrical and physical conversion. But, unlike traditional media converters, they also provide Layer 2 services—in other words, they’re really switches. This kind of media converter often has more than two ports, enabling you to, for instance, extend two or more copper links across a single fiber link. They also often feature autosensing ports on the copper side, making them useful for linking segments operating at different speeds.

Media converters are available in standalone models that convert between two different media types and in chassis-based models that connect many different media types in a single housing.

Rent an apartment

Standalone converters convert between two media. But, like a small apartment, they can be outgrown. Consider your current and future applications before selecting a media converter. Standalone converters are available in many configurations, including 10BASE-T to multimode or single-mode fiber, 10BASE-T to Thin coax (ThinNet), 10BASE-T to thick coax (standard Ethernet), CDDI to FDDI, and Thin coax to fiber. 100BASE-T and 100BASE-FX models that connect UTP to single- or multimode fiber are also available. With the development of Gigabit Ethernet (1000 Mbps), media converters have been created to make the transition to high-speed networks easier.

...or buy a house.

Chassis-based or modular media converters are normally rackmountable and have slots that house media converter modules. Like a well-planned house, the chassis gives you room to grow. These are used when many Ethernet segments of different media types need to be connected in a central location. Modules are available for the same conversions performed by the standalone converters, and 10BASE-T, 100BASE-TX, 100BASE-FX, and Gigabit modules may also be mixed.


Black Box Explains...Straight-pinned and crossover cable.

Straight-pinned cable has the most common type of pinning. The send and receive pairs are wired straight-through on either end of the cable.

Crossover cable is generally used for peer-to-peer connections.... more/see it nowThe send and receive pairs are crossed between Connector A to Connector B on either end of the cable. collapse

Black Box Explains...USB.

What is USB?
Universal Serial Bus (USB) is a royalty-free bus specification developed in the 1990s by leading manufacturers in the PC and telephony industries to support plug-and-play peripheral connections. USB... more/see it nowhas standardized how peripherals, such as keyboards, disk drivers, cameras, printers, and hubs) are connected to computers.

USB offers increased bandwidth, isochronous and asynchronous data transfer, and lower cost than older input/output ports. Designed to consolidate the cable clutter associated with multiple peripherals and ports, USB supports all types of computer- and telephone-related devices.

Universal Serial Bus (USB) USB detects and configures the new devices instantly.
Before USB, adding peripherals required skill. You had to open your computer to install a card, set DIP switches, and make IRQ settings. Now you can connect digital printers, recorders, backup drives, and other devices in seconds. USB detects and configures the new devices instantly.

Benefits of USB.
• USB is “universal.” Almost every device today has a USB port of some type.
• Convenient plug-and-play connections. No powering down. No rebooting.
• Power. USB supplies power so you don’t have to worry about adding power. The A socket supplies the power.
• Speed. USB is fast and getting faster. The original USB 1.0 had a data rate of 1.5 Mbps. USB 3.0 has a data rate of 4.8 Gbps.

USB Standards

USB 1.1
USB 1.1, introduced in 1995, is the original USB standard. It has two data rates: 12 Mbps (Full-Speed) for devices such as disk drives that need high-speed throughput and 1.5 Mbps (Low-Speed) for devices such as joysticks that need much lower bandwidth.

USB 2.0
In 2002, USB 2.0, (High-Speed) was introduced. This version is backward-compatible with USB 1.1. It increases the speed of the peripheral to PC connection from 12 Mbps to 480 Mbps, or 40 times faster than USB 1.1.

This increase in bandwidth enhances the use of external peripherals that require high throughput, such as printers, cameras, video equipment, and more. USB 2.0 supports demanding applications, such as Web publishing, in which multiple high-speed devices run simultaneously.

USB 3.0
USB 3.0 (SuperSpeed) (2008) provides vast improvements over USB 2.0. USB 3.0 has speeds up to 5 Gbps, nearly ten times that of USB 2.0. USB 3.0 adds a physical bus running in parallel with the existing 2.0 bus.

USB 3.0 is designed to be backward compatible with USB 2.0.

USB 3.0 Connector
USB 3.0 has a flat USB Type A plug, but inside there is an extra set of connectors and the edge of the plug is blue instead of white. The Type B plug looks different with an extra set of connectors. Type A plugs from USB 3.0 and 2.0 are designed to interoperate. USB 3.0 Type B plugs are larger than USB 2.0 plugs. USB 2.0 Type B plugs can be inserted into USB 3.0 receptacles, but the opposite is not possible.

USB 3.0 Cable
The USB 3.0 cable contains nine wires—four wire pairs plus a ground. It has two more data pairs than USB 2.0, which has one pair for data and one pair for power. The extra pairs enable USB 3.0 to support bidirectional asynchronous, full-duplex data transfer instead of USB 2.0’s half-duplex polling method.

USB 3.0 Power
USB 3.0 provides 50% more power than USB 2.0 (150 mA vs 100 mA) to unconfigured devices and up to 80% more power (900 mA vs 500 mA) to configured devices. It also conserves power too compared to USB 2.0, which uses power when the cable isn’t being used.

USB 3.1
Released in 2013, is called SuperSpeed USB 10 Gbps. There are three main differentiators to USB 3.1. It doubles the data rate from 5 Gbps to 10 Gbps. It will use the new, under-development Type C connector, which is far smaller and designed for use with everything from laptops to mobile phones. The Type C connector is being touted as a single-cable solution for audio, video, data, and power. It will also have a reversible plug orientation. Lastly, will have bidirectional power delivery of up to 100 watts and power auto-negotiation. It is backward compatible with USB 3.0 and 2.0, but an adapter is needed for the physical connection.

Transmission Rates
USB 3.0: 4.8 Gbps
USB 2.0: 480 Mbps
USB 1.1: 12 Mbps

Cable Length/Node
5 meters (3 meters for 3.0 devices requiring higher speeds).
Devices/bus: 127
Tier/bus: 5

Black Box Explains...What to look for in a channel solution.

Channel solution. You hear the term a lot these days to describe complete copper or fiber cabling systems. But what exactly is a channel solution and what are its benefits?... more/see it now

A definition.
A channel solution is a cabling system from the data center to the desktop where every cable, jack, and patch panel is designed to work together and give you consistent end-to-end performance when compared with the EIA/TIA requirements.

Its benefits.
A channel solution is beneficial because you have some assurance that your cabling components will perform as specified. Without that assurance, one part may not be doing its job, so your entire system may not be performing up to standard, which is a problem — especially if you rely on bandwidth-heavy links for video and voice.

What to look for.
There are a lot of channel solutions advertised on the Internet and elsewhere. So what exactly should you be looking for?

For one, make sure it’s a fully tested, guaranteed channel solution. The facts show an inferior cabling system can cause up to 70 percent of network downtime — even though it usually represents only 5 percent of an initial network investment. So don’t risk widespread failure by skimping on a system that doesn’t offer guaranteed channel performance. You need to make sure the products are engineered to meet or go beyond the key measurements for CAT5e or CAT6 performance.

And, sure, they may be designed to work together, but does the supplier absolutely guarantee how well they perform as part of a channel — end to end? Don’t just rely on what the supplier says. They may claim their products meet CAT5e or CAT6 requirements, but the proof is in the performance. Start by asking if the channel solution is independently tested and certified by a reputable third party. There are a lot of suppliers out there who don’t have the trademarked ETL approval logo, for example.

What ETL Verified means.
The ETL logo certifies that a channel solution has been found to be in compliance with recognized standards. To ensure consistent top quality, Black Box participates in independent third-party testing by InterTek Testing Services/ETL Semko, Inc. Once a quarter, an Intertek inspector visits Black Box and randomly selects cable and cabling products for testing.

The GigaTrue® CAT6 and GigaBase® CAT5e Solid Bulk Cable are ETL Verified at the component level to verify that they conform to the applicable industry standards. The GigaTrue® CAT6 and GigaBase® CAT5e Channels, consisting of bulk cable, patch cable, jacks, patch panels, and wiring blocks, are tested and verified according to industry standards in a LAN environment under InterTek’s Cabling System Channel Verification Program. For the latest test results, contact our FREE Tech Support. collapse

Black Box Explains...Solid vs. stranded cable.

Solid-conductor cable is designed for backbone and horizontal cable runs. Use it for runs between two wiring closets or from the wiring closet to a wallplate. Solid cable shouldn’t be... more/see it nowbent, flexed, or twisted repeatedly. Its attenuation is lower than that of stranded-conductor cable.

Stranded cable is for use in shorter runs between network interface cards (NICs) and wallplates or between concentrators and patch panels, hubs, and other rackmounted equipment. Stranded-conductor cable is much more flexible than solid-core cable. However, attenuation is higher in stranded-conductor cable, so the total length of stranded cable in your system should be kept to a minimum to reduce signal degradation. collapse

Black Box Explains...Layer 2, 3, and 4 switches.

...more/see it now
OSI Layer Physical
7-Application Applicaton Software

LAN-Compatible Software
E-Mail, Diagnostics, Word Processing, Database

Network Applications
6-Presentation Data-
Conversion Utilities
Vendor-Specific Network Shells and Gateway™ Workstation Software
5-Session Network Operating System SPX NetBIOS DECnet™ TCP/IP AppleTalk®
4-Transport Novell® NetWare® IPX™ PC LAN LAN Mgr DECnet PC/TCP® VINES™ NFS TOPS® Apple
3-Network Control
2-Data Link Network E A TR P TR E TR E E E P E P
1-Physical E=Ethernet; TR=Token Ring; A=ARCNET®; P=PhoneNET®

With the rapid development of computer networks over the last decade, high-end switching has become one of the most important functions on a network for moving data efficiently and quickly from one place to another.

Here’s how a switch works: As data passes through the switch, it examines addressing information attached to each data packet. From this information, the switch determines the packet’s destination on the network. It then creates a virtual link to the destination and sends the packet there.

The efficiency and speed of a switch depends on its algorithms, its switching fabric, and its processor. Its complexity is determined by the layer at which the switch operates in the OSI (Open Systems Interconnection) Reference Model (see above).

OSI is a layered network design framework that establishes a standard so that devices from different vendors work together. Network addresses are based on this OSI Model and are hierarchical. The more details that are included, the more specific the address becomes and the easier it is to find.

The Layer at which the switch operates is determined by how much addressing detail the switch reads as data passes through.

Switches can also be considered low end or high end. A low-end switch operates in Layer 2 of the OSI Model and can also operate in a combination of Layers 2 and 3. High-end switches operate in Layer 3, Layer 4, or a combination of the two.

Layer 2 Switches (The Data-Link Layer)

Layer 2 switches operate using physical network addresses. Physical addresses, also known as link-layer, hardware, or MAC-layer addresses, identify individual devices. Most hardware devices are permanently assigned this number during the manufacturing process.

Switches operating at Layer 2 are very fast because they’re just sorting physical addresses, but they usually aren’t very smart—that is, they don’t look at the data packet very closely to learn anything more about where it’s headed.

Layer 3 Switches (The Network Layer)

Layer 3 switches use network or IP addresses that identify locations on the network. They read network addresses more closely than Layer 2 switches—they identify network locations as well as the physical device. A location can be a LAN workstation, a location in a computer’s memory, or even a different packet of data traveling through a network.

Switches operating at Layer 3 are smarter than Layer 2 devices and incorporate routing functions to actively calculate the best way to send a packet to its destination. But although they’re smarter, they may not be as fast if their algorithms, fabric, and processor don’t support high speeds.

Layer 4 Switches (The Transport Layer)

Layer 4 of the OSI Model coordinates communications between systems. Layer 4 switches are capable of identifying which application protocols (HTTP, SNTP, FTP, and so forth) are included with each packet, and they use this information to hand off the packet to the appropriate higher-layer software. Layer 4 switches make packet-forwarding decisions based not only on the MAC address and IP address, but also on the application to which a packet belongs.

Because Layer 4 devices enable you to establish priorities for network traffic based on application, you can assign a high priority to packets belonging to vital in-house applications such as Peoplesoft, with different forwarding rules for low-priority packets such as generic HTTP-based Internet traffic.

Layer 4 switches also provide an effective wire-speed security shield for your network because any company- or industry-specific protocols can be confined to only authorized switched ports or users. This security feature is often reinforced with traffic filtering and forwarding features.


Black Box Explains...Loose-tube vs. tight-buffered fiber optic cable.

There are two styles of fiber optic cable construction: loose tube and tight buffered. Both contain some type of strengthening member, such as aramid yarn, stainless steel wire strands, or... more/see it noweven gel-filled sleeves. But each is designed for very different environments.

Loose tube cables, the older of the two cable types, are specifically designed for harsh outdoor environments. They protect the fiber core, cladding, and coating by enclosing everything within semi-rigid protective sleeves or tubes. In loose-tube cables that hold more than one optical fiber, each individually sleeved core is bundled loosely within an all-encompassing outer jacket.

Many loose-tube cables also have a water-resistant gel that surrounds the fibers. This gel helps protect them from moisture, so the cables are great for harsh, high-humidity environments where water or condensation can be a problem. The gel-filled tubes can expand and contract with temperature changes, too.

But gel-filled loose-tube cables are not the best choice when cable needs to be submerged or where it’s routed around multiple bends. Excess cable strain can force fibers to emerge from the gel.

Tight-buffered cables, in contrast, are optimized for indoor applications. Because they’re sturdier than loose-tube cables, they’re best suited for moderate-length LAN/WAN connections, long indoor runs, and even direct burial. Tight-buffered cables are also recommended for underwater applications.

Instead of a gel layer or sleeve to protect the fiber core, tight-buffered cables use a two-layer coating. One is plastic; the other is waterproof acrylate. The acrylate coating keeps moisture away from the cable, like the gel-filled sleeves do for loose-tube cables. But this acrylate layer is bound tightly to the plastic fiber layer, so the core is never exposed (as it can be with gel-filled cables) when the cable is bent or compressed underwater.

Tight-buffered cables are also easier to install because there’s no messy gel to clean up and they don’t require a fan-out kit for splicing or termination. You can crimp connectors directly to each fiber.

Want the best of both worlds? Try a hybrid, breakout-style fiber optic cable, which combines tight-buffered cables within a loose-tube housing. collapse

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