Black Box Explains...Wireless Ethernet standards.
The precursor to 802.11b, IEEE 802.11 was introduced in 1997. It was a beginning, but 802.11 only supported speeds up to 2 Mbps. And it supported two entirely different... more/see it nowmethods of encodingFrequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS). This led to confusion and incompatibility between different vendors equipment.
802.11b is comfortably established as the most popular wireless standard. With the IEEE 802.11b Ethernet standard, wireless is fast, easy, and affordable. Wireless devices from all vendors work together seamlessly. 802.11b is a perfect example of a technology that has become both sophisticated and standardized enough to really make life simpler for its users.
The 802.11b extension of the original 802.11 standard boosts wireless throughput from 2 Mbps all the way up to 11 Mbps. 802.11b can transmit up to 200 feet under good conditions, although this distance may be reduced considerably by the presence of obstacles such as walls.
This standard uses DSSS. With DSSS, each bit transmitted is encoded and the encoded bits are sent in parallel across an entire range of frequencies. The code used in a transmission is known only to the sending and receiving stations. By transmitting identical signals across the entire range of frequencies, DSSS helps to reduce interference and makes it possible to recover lost data without retransmission.
The 802.11a wireless Ethernet standard is new on the scene. It uses a different band than 802.11b—the 5.8-GHz band called U-NII (Unlicensed National Information Infrastructure) in the United States. Because the U-NII band has a higher frequency and a larger bandwidth allotment than the 2.4-GHz band, the 802.11a standard achieves speeds of up to 54 Mbps. However, its more limited in range than 802.11b. It uses an orthogonal frequency-division multiplexing (OFDM) encoding scheme rather than FHSS or DSSS.
802.11g is an extension of 802.11b and operates in the same 2.4-GHz band as 802.11b. It brings data rates up to 54 Mbps using OFDM technology.
Because it's actually an extension of 802.11b, 802.11g is backward-compatible with 802.11b—an 802.11b device can interface directly with an 802.11g access point. However, because 802.11g also runs on the same three channels as 802.11b, it can crowd already busy frequencies.
Super G® is a subset of 802.11g and is a proprietary extension of the 802.11g standard that doubles throughput to 108 Mbps. Super G is not an IEEE approved standard. If you use it, you should use devices from one vendor to ensure compatibility. Super G is generally backwards compatible with 802.11g.
80211n improves upon 802.11g significantly with an increase in the data rate to 600 Mbps. Channels operate at 40 MHz doubling the channel width from 20 MHz. 802.11n operates on both the 2.4 GHz and the 5 GHz bands. 802.11n also added multiple-input multiple-output antennas (MIMO) collapse
Black Box Explains...Types of KVM switches.
Black Box has the keyboard/video switches you need to share one CPU between several workstations or to control several CPUs from one monitor and keyboard.
If you do a lot of... more/see it nowswitching, you need premium switches—our top-of-the-line ServSwitch™ KVM switches give you the most reliable connections for the amount of KVM equipment supported. With ServSwitch KVM switches, you can manage as many CPUs as you want from just one workstation, and you can access any server in any computer room from any workstation. Eliminating needless equipment not only saves you money, it also gives you more space and less clutter. Plus, you can switch between PCs, Sun®, and Mac® CPUs. ServSwitch KVM switches can also cut your electricity and cooling costs because by sharing monitors, you use less power and generate less heat.
If your switching demands are very minor, you may not need products as advanced as ServSwitch. Black Box offers switches to fill less demanding needs. Most of these are manual switches or basic electronic switches, which don’t have the sophisticated emulation technology used by the ServSwitch.
For PCs with PS/2® keyboards, try our Keyboard/Video Switches. They send keyboard signals, so your CPUs boot up as though they each have their own keyboard.
With the RS/6000™ KVM Switch, you can run up to six RS/6000 servers from one workstation. Our Keyboard/ Video Switch for Mac enables you to control up to two Mac CPUs from one keyboard and monitor.
With BLACK BOX® KVM Switches, you can share a workstation with two or four CPUs. They’re available in IBM® PC and Sun Workstation® configurations.
You’ll also find that our long-life manual Keyboard/Video Switches are perfect for basic switching applications. collapse
Black Box Explains...Digital Visual Interface (DVI) connectors.
The DVI (Digital Video Interface) technology is the standard digital transfer medium for computers while the HDMI interface is more commonly found on HDTVs, and other high-end displays.
The Digital... more/see it nowVisual Interface (DVI) standard is based on transition-minimized differential signaling (TMDS). There are two DVI formats: Single-Link and Dual-Link. Single-link cables use one TMDS-165 MHz transmitter and dual-link cables use two. The dual-link cables double the power of the transmission. A single-link cable can transmit a resolution ?of 1920 x 1200 vs. 2560 x 1600 for a dual-link cable.
There are several types of connectors: ?DVI-D, DVI-I, DVI-A, DFP, and EVC.
- DVI-D is a digital-only connector for use between a digital video source and monitors. DVI-D eliminates analog conversion and improves the display. It can be used when one or both connections are DVI-D.
- DVI-I (integrated) supports both digital and analog RGB connections. It can transmit either a digital-to-digital signals or an analog-to-analog signal. It is used by some manufacturers on products instead of separate analog and digital connectors. If both connectors are DVI-I, you can use any DVI cable, but a DVI-I is recommended.
- DVI-A (analog) is used to carry an DVI signal from a computer to an analog VGA device, such as a display. If one or both of your connections are DVI-A, use this cable. ?If one connection is DVI and the other is ?VGA HD15, you need a cable or adapter ?with both connectors.
- DFP (Digital Flat Panel) was an early digital-only connector used on some displays.
- EVC (also known as P&D, for ?Plug & Display), another older connector, handles digital and analog connections.
Black Box Explains... Matrix video switches.
Matrix switches enable computers to mix and match the output of multiple PCs on multiple video monitors.
For instance, if your operation has four PCs and you want to display the... more/see it nowvideo on one monitor to the other three monitors, a matrix video switch is what you need to handle the job. Use matrix switches for:
• Trade showsSet up a wall of video to wow the senses of attendees.
• Transportation schedulesProvide real-time updates of flights or deliveries on multiple screens.
• Training demonstrationsControl each screens video to focus everyones attention on whats important. collapse