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...Cable management.
Corporate networks are complex systems of PCs, servers, printers, and the devices that connect them. Getting everything to work in harmony requires bundles of cables, and managing all those cables... more/see it nowfrom inside a telecommunications closet can be a daunting task. To connect cable bundles to rackmounted equipment (like patch panels, hubs, switches, or routers), you need to direct the bundles overhead, vertically, and horizontally.
A popular choice for overhead cable routing is a ladder rack. Ladder racks come in many varieties. They can run along a wall supported by brackets or they can be installed overhead and supported by a threaded rod. Ladder racks can support large cable bundles neatly and safely. Because bundles lie flat on a ladder rack, cables aren’t subjected to harsh bends. You can run ladder racks directly to the top of most standard telecommunications racks that conform to TIA/EIA standards.
Use vertical cable managers to route cable bundles along the sides of a rack. These “cable troughs” as they’re sometimes called can be single sided—or double sided to route cable bundles to the rear of equipment and to the ports on the front as well. Vertical cable managers usually come with some type of protection for the cable, such as grommeted holes to protect the cable jacket or a cover that may clip on or act as a door.
Horizontal cable managers are usually a series of rings that directs cables in an orderly fashion toward the ports of hubs, switches, and patch panels. collapse
Black Box Explains...Remote power control.
Simply put, remote power control is the ability to reset or reboot PC, LAN, telecom, and other computer equipment without being at the equipments location.
Who needs remote power control?... more/see it nowAny organization with a network that reaches remote sites. This can include branch offices, unmanned information kiosks, remote monitoring stations, alarm and control systems, and even HVAC systems.
When equipment locks up at remote sites, it is usually up to the system manager at headquarters to reset it. Often, there arent any technically trained personnel at the remote site who can perform maintenance and resets on equipment. So, in order to save traveling time and minimize downtime, remote power control enables the system manager to take care of things at the office without ever leaving home!
Remote power control can be done with modems or existing or special phone lines. The ideal system uses out-of-band management, an alternate path over an ordinary dialup line that doesnt interfere with network equipment.
An effective remote power control system incorporates the following:
• An existing phone line, such as a line being used for a fax, modem, or phone.
• Transparent operation. The system shouldnt interfere with or be affected by normal calls.
• Security features. The system should prevent unauthorized access to network equipment.
• Flexibility. System managers should be able to dial in from anywhere and control mulitple devices with one call.
• Have power control devices that meet UL® and FCC requirements. collapse
Black Box Explains... Plasma vs. LCD Screens
When deciding whether to use plasma or liquid crystal diode (LCD) displays for your applications, you need to consider many factors. Both provide brilliant color, sharp text contrast, and crystal-clear... more/see it nowimages. But the way in which plasma and LCD screens process and display incoming video/computer signals is markedly different.
Compare and contrast.
Both plasma and LCD technology provide stark enough contrasts to make displays sharp and pleasing. But when it comes to contrast output, plasma technology outperforms LCD screens. Some plasma displays have a 3000:1 contrast ratio, which is the measure of the blackest black compared to the whitest white. LCDs use electric charges to untwist liquid crystals, thereby blocking light and emitting darker pixels. Despite this process, LCD displays dont produce more than a 1000:1 contrast ratio.
Clarity thats light waves ahead.
Pixels contain enough information to produce every color in the spectrum. Because plasmas use each and every pixel on their screens, color information is reproduced more accurately. Plasma screens display moving images with remarkable clarity, though burn-in can be an issue. For displays with lots of light and dark imagery, plasma panels provide excellent performance with their high-contrast levels, color saturation, and overall brightness.
LCD displays, on the other hand, manipulate light waves and reproduce colors by subtracting colors from white light. Though this makes it more difficult to maintain color accuracy and vibrancy compared to plasma screens, LCDs have an advantage with their higher-than-average number of pixels per square inch. These additional pixels make LCD technology better at displaying static images from computers or VGA sources in full-color detail. Plus, theres no flicker and very little screen burn-in.
Applications with large amounts of data—such as those found on spreadsheets—display particularly well on LCD monitors.
Brilliant displays that go on and on.
With LCD screens, there are essentially no parts to wear out. LCD screens last as long as their backlights do, with displays lasting, on average, 50,000–75,000 hours. Thats why LCD screens are especially good for long-term applications, such as digital signage or displays that require around-the-clock use.
Plasma screens, however, use a combination of electric currents and noble gases (argon, neon, and xenon) to produce a glow, which in turn yields brilliant color. The half-life of these gases, however, is only around 25,000 hours. The glow they produce grows dimmer over time.
The right angle can make all the difference.
Plasmas light every pixel on the screen, making the brightness on the screen consistent and giving plasmas the edge when it comes to viewing angles. In fact, plasma screens have as much as a 160° viewing angle compared to LCDs. This makes viewing the images on the screen easier to see from a variety of angles. In doing so, however, plasmas consume much more power.
LCDs display at 130–140° angles, but their use of fluorescent backlighting requires much less power to operate than plasmas. This also makes LCDs less prone to burn-in or ghosting of images.
Black Box Explains… Category 7/Class F.
Category 7/Class F (ISO/IEC 11801:2002) specifies a frequency range of 1–600 MHz over 100 meters of fully shielded twisted-pair cabling. It encompasses four individually shielded pairs inside an overall shield,... more/see it nowcalled Shielded/Foiled Twisted Pair (S/FTP) or Foiled/ Foiled Twisted Pair (F/FTP). There is a pending class Fa, based on the use of S/FTP cable to 1000 MHz. It can support 10GBASE-T transmissions.
With both types of cable, each twisted pair is enclosed in foil. In S/FTP cable, all four pairs are encased in an overall metal braid. In F/FTP, the four pairs are encased in foil.
Category 7/Class F cable can be terminated with two interface designs as specified in IEC 6063-7-7 and IEC 61076-3-104. One is an RJ-45 compatible GG-45 connector. The other is the more common TERA connector, which was launched in 1999.
Category 7/Class F is backwards compatible with traditional CAT6 and CAT5 cable, but it has far more stringent specifications for crosstalk and system noise. The fully shielded cable virtually eliminates crosstalk between the pairs. In addition, the cable is noise resistant, which makes the Category 7/Class F systems ideal for high EMI areas, such as industrial and medical imaging facilities.
Category 7/Class F cable can also increase security by preventing the emission of data signals from the cable to nearby areas. collapse
Black Box Explains...High-speed networking.
What are my choices for high-speed
... more/see it nownetworking?
| 100BASE-T | ATM
| Gibabit Ethernet
Switched Ethernet relies on centralized multiport switches
to provide a physical link between multiple LAN segments.
Inside each intelligent switch, high-speed circuitry supports
wire-speed virtual connections between all the segments
for maximum bandwidth allocation on demand. Adding new segments
to a switch increases the aggregate network speed while
reducing overall congestion, so Switched Ethernet provides
superior configuration flexibility. It also gives you an
excellent migration path from 10- to 100-Mbps Ethernet,
since both segments can often operate via the same switch.
Benefits of Switched Ethernet—It’s
a cost-effective technique for increasing the overall network
throughput and reducing congestion on a 10-Mbps network.
Other than the addition of the switching hub, the Ethernet
network remains the same—the same network interface
cards, the same client software, the same LAN cabling.
100BASE-T retains the familiar CSMA/CD media access technique
used in 10-Mbps Ethernet networks. It also supports a broad
range of cabling options: two standards for twisted pair
and one for fiber. 100BASE-TX supports 2-pair Category 5
UTP or Type 1 STP cable. 100BASE-FX enables fiber optic
links via duplex multimode fiber cable.
Benefits of 100BASE-T—It
retains CSMA/CD, so existing network management systems
don’t need to be rewritten. It can easily be integrated
into existing 10-Mbps Ethernet LANs, so your previous investment
is saved (see Figures 1 and 2).
It’s also backed by hundreds of manufacturers in the
high-speed networking industry, including Black Box!
||100BASE-T (IEEE 802.3u)
of this Standard
||Category 5 (2-Pair)
||Duplex Multimode or Single-Mode
|| Category 5—100
||Backbone using Ethernet
switches to provide increased throughput. Small to medium
workgroups using applications (i.e. CAD, CAM) that output
huge data files.
Asynchronous Transfer Mode (ATM) is a cell-based fast-packet
communication technique that supports data-transfer rates
ranging from sub-T1 speeds (less than 1.544 Mbps) up to
Like other packet-switching services (Frame Relay, SMDS),
ATM achieves its high speeds in part by transmitting data
in fixed-size cells and dispensing with error-correction
protocols. Instead, it relies on the inherent integrity
of digital lines to ensure data integrity.
Benefits of ATM—Networks
are extremely versatile. An ATM network can be treated as
a single network, whether it connects points in a building
or across the country. Its fixed-length cell-relay operation,
the signaling technology of the future, offers more predictable
performance than variable-length frames. And it can be integrated
into an existing network as needed without having to upgrade
the entire LAN.
Like Ethernet and Fast Ethernet before it, Gigabit Ethernet
works with earlier versions of the IEEE 802.3 standard—both
10 and 100 Mbps— although some equipment will need
to be upgraded. The Gigabit Ethernet standard (IEEE 802.3z)
was approved in June 1998, and its speed of 1 Gbps is a
tenfold increase over Fast Ethernet.
There are two basic types of Gigabit Ethernet: shared
and switched. Shared Gigabit Ethernet
is a higher-speed version of 10/100BASE-T using CSMA/CD
Medium Access Control. Switched Gigabit Ethernet uses Logical
Link Control (LLC). Gigabit Ethernet increases frame sizes
from 64 bytes to 512 bytes minimum, and from 1514 bytes
to 9000 bytes maximum.
Benefits of Gigabit Ethernet—It
solves bandwidth problems. Its primary use is for backbones.
The medium is fiber or Category 5e 100-ohm cable. collapse
Black Box Explains... KVM IP gateways
Just as a gate serves as an entry or exit point to a property, a gateway serves the same purpose in the networking world. It’s the device that acts as... more/see it nowa network entrance or go-between for two or more networks.
There are different types of gateways, depending on the network.
An application gateway converts data or commands from one format to another. A VoIP gateway converts analog voice calls into VoIP packets. An IP gateway is like a media gateway, translating data from one telecommunications device to another.
Gateways often include other features and devices, such as protocol converters, routers, firewalls, encryption, voice compression, etc. Although a gateway is an essential feature of most routers, other devices, such as a PC or server, can also function as a gateway.
A KVMoIP switch contains an IP gateway, which is the pathway the KVM signals use to travel from the IP network to an existing non-IP KVM switch. It converts and directs the KVM signals, giving a user access to and control of an existing non-IP KVM switch over the Internet. collapse
Black Box Explains...Fiber connectors.
• The ST® connector, which uses a bayonet locking system, is the most common connector.
• The SC connector features a molded body and a push- pull locking system.
• The FDDI... more/see it nowconnector comes with a 2.5-mm free-floating ferrule and a fixed shroud to minimize light loss.
• The MT-RJ connector, a small-form RJ-style connector, features a molded body and uses cleave-and-leave splicing.
• The LC connector, a small-form factor connector, features a ceramic ferrule and looks like a mini SC connector.
• The VF-45™connector is another small-form factor connector. It uses a unique V-groove design.
• The FC connector is a threaded body connector. Secure it by screwing the connector body to the mating threads. Used in high-vibration environments.
• The MTO/MTP connector is a fiber connector that uses high-fiber-count ribbon cable. Its used in high-density fiber applications.
• The MU connector resembles the larger SC connector. It uses a simple push-pull latching connection and is well suited for high-density applications.
Black Box Explains…Component vs. channel testing.
When using a Category 6 system, the full specification includes the testing of each part individually and in an end-to-end-channel. Because CAT6 is an open standard, products from different vendors... more/see it nowshould work together.
Channel testing includes patch cable, bulk cable, jacks, patch panels, etc. These tests cover a number of measurements, including: attenuation, NEXT, PS-NEXT, EL-FEXT, ACR, PS-ACR, EL-FEXT, PS-ELFEXT, and Return Loss. Products that are tested together should work together as specified. In theory, products from all manufacturers are interchangeable. But, if products from different manufacturers are inserted in a channel, end-to-end CAT6 performance may be compromised.
Component testing, on the other hand, is much stricter even though only two characteristics are measured: crosstalk and return loss. Although all CAT6 products should be interchangeable, products labeled as component are guaranteed to perform
to a CAT6 level in a channel with products from different manufacturers.
For more information on cable, channel, and component specs, see below.
Buyer’s Guide: CAT5e vs. CAT6 Cable
Standard — CAT5e: TIA-568-B.2; CAT6: TIA-568-B.2-1
Frequency — CAT5e: 100 MHz; CAT6: 250 MHz
Attenuation (maximum at 100 MHz) —
Cable: CAT5e: 22 dB; CAT6: 19.8 dB
Connector: CAT5e: 0.4 dB; CAT6: 0.2 dB
Channel: CAT5e: 24.0 dB; CAT6: 21.3 dB
NEXT (minimum at 100 MHz) —
Cable: CAT5e: 35.3 dB; CAT6: 44.3 dB
Connector: CAT5e: 43.0 dB; CAT6: 54.0 dB
Channel: CAT5e: 30.1 dB; CAT6: 39.9 dB
PS-NEXT (minimum at 100 MHz) — 32.3 dB 42.3 dB
EL-FEXT (minimum at 100 MHz) —
Cable: CAT5e: 23.8 dB; CAT6: 27.8 dB
Connector: CAT5e: 35.1 dB; CAT6: 43.1 dB
Channel: CAT5e: 17.4 dB; CAT6: 23.3 dB
PS-ELFEXT (minimum at 100 MHz) — CAT5e: 20.8 dB; CAT6: 24.8 dB
Return Loss (minimum at 100 MHz) —
Cable: CAT5e: 20.1 dB; CAT6: 20.1 dB
Connector: CAT5e: 20.0 dB: CAT6: 24.0 dB
Channel: CAT5e: 10.0 dB; CAT6: 12.0 dB
Characteristic Impedance — Both: 100 ohms ± 15%
Delay Skew (maximum per 100 m) — Both: 45 ns
NOTE: In Attenuation testing, the lower the number, the better. In NEXT, EL-FEXT, and Return Loss testing, the higher the number, the better.
Black Box Explains...Using repeaters to extend your network.
A repeater is a signal regenerator. It amplifies and regenerates received data and relays data from one length of cable to another—this can be between two segments of the same... more/see it nowcable type (such as UTP to UTP) or between two lengths of entirely different cable types (such as UTP to ThinNet). Because repeaters operate at the Data Link layer of the OSI model, having too many repeaters on a network introduces delays and causes problems with signal timing. Ethernet allows a maximum of two IRLs (InterRepeater Links) between any two devices and up to four per network. A hub also counts as a repeater. (If simple media conversion is your goal, use media converters instead. For details, contact Tech Suport.)
Repeaters boost distance by amplifying the signal.
A repeater actually regenerates and amplifies the signal to gain distance. The repeater not only changes the media type, it also gives the signal a boost to send it over a longer distance.
Repeaters boost distance through a change in media.
In addition to amplifying the signal, a repeater can also add distance to your network by enabling you to change to a media type such as fiber that supports longer distances. collapse