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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...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...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.

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Black Box Explains...Modem eliminators.

Understanding the process of elimination.
If your office environment has sync equipment, and if that equipment is also used for local data communications, you should consider replacing those modems with cost-effective... more/see it nowand versatile modem eliminators.

What does a modem eliminator do?
One modem eliminator can connect a local terminal and computer port in lieu of the pair of modems that they would normally connect to. Plus, a modem eliminator enables DCE-to-DTE data and control-signal connections that are not easily achieved by standard cables or connectors in a sync environment.

Basically, a modem eliminator simulates a sync data link. It does this two ways. First, it provides clocking, which is mandatory for sync devices to communicate. Second, it provides the handshaking that DCEs do.

Why should you use a modem eliminator?
One—if you have two sync DTEs in the same room or close to each other, you will need a modem eliminator.

Two—if you have a network with routers, you just found the perfect equipment tester.

A modem eliminator can enable in-house bench testing of routers or existing equipment. There’s no need to place routers all over your network only to find out they don’t work once you test the LAN. A modem eliminator tells you what equipment passes your tests before you install.

Three—a modem eliminator makes good economic sense. One does the job of two modems—and it does the job better. You get a high return on your investment. 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...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
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Black Box Explains...Connecting peripherals with USB.

Before Universal Serial Bus (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... more/see it nowdigital joysticks, scanners, speakers, cameras, or PC telephones to your computer instantly. With USB, anyone can make the connection because everything is automatic!

Because USB connections are hot-swappable, you can attach or remove peripherals without shutting down your computer. Also, USB hubs have additional ports that enable you to daisychain multiple devices together. More than 800 leading PC, peripheral, and software manufacturers support USB. collapse


Black Box Explains... Spread Spectrum wireless technology.

Frequency-Hopping Spread Spectrum wireless communication provides error-free transmission, top security, and high levels of throughput without the need for an FCC site license. The key to Spread Spectrum is a... more/see it nowfrequency-hopping transceiver.

Narrow-band frequency hoppers use a predefined algorithm to maintain synchronization and high throughput between master and remote modems. They achieve this by continually switching or “hopping” from one transmission frequency to another throughout the Spread Spectrum band. The sequence of frequencies is very difficult to predict and thus nearly impossible to eavesdrop on or jam. If interference is encountered at any particular frequency, the built-in error correction detects it and resends the data packet at the next frequency hop. Because EMI/RFI interference rarely affects the entire available bandwidth, and each frequency hop is at least 6 MHz, the radio transmitter has access to as many as 100 frequencies within the spectrum to avoid interference and ensure that data gets through. collapse


Black Box Explains... Advantages of the MicroRACK system.

• Midplane architecture—Separate front and rear cards make changing interfaces easy.
• Multiple functions—Supports line drivers, interface converters, fiber modems, CSU/DSUs, and synchronous modem eliminators.
• Hot swappable—MicroRACK Cards can be replaced... more/see it nowwithout powering down, so you cut your network’s downtime.
• Two-, four-, and eight-port MicroRACKs—available for smaller or desktop installations. They’re just right for tight spaces that can’t accommodate a full-sized (16-port) rack.
• Optional dual cards—Some Mini Driver Cards have two drivers in one card. One MicroRACK chassis can hold up to 32 Mini Drivers!
• All standard connections available—DB25, RJ-11, RJ-45, fiber, V.35.
• Choose you own power supply—120–240 VAC, 12 VDC, 24 VDC, or 48 VDC. collapse

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