Black Box Explains... Printer Sharing with Windows
Unlike the earlier DOS operating systems, Windows® doesnt 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 doesnt 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 its 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
Black Box Explains...PC, UPC, and APC fiber connectors.
Fiber optic cables have different types of mechanical connections. The type of connection determines the quality of the fiber optic lightwave transmission. The different types well discuss here are the... more/see it nowflat-surface, Physical Contact (PC), Ultra Physical Contact (UPC), and Angled Physical Contact (APC).
The original fiber connector is a flat-surface connection, or a flat connector. When mated, an air gap naturally forms between the two surfaces from small imperfections in the flat surfaces. The back reflection in flat connectors is about -14 dB or roughly 4%.
As technology progresses, connections improve. The most common connection now is the PC connector. Physical Contact connectors are just thatthe end faces and fibers of two cables actually touch each other when mated.
In the PC connector, the two fibers meet, as they do with the flat connector, but the end faces are polished to be slightly curved or spherical. This eliminates the air gap and forces the fibers into contact. The back reflection is about -40 dB. This connector is used in most applications.
An improvement to the PC is the UPC connector. The end faces are given an extended polishing for a better surface finish. The back reflection is reduced even more to about -55 dB. These connectors are often used in digital, CATV, and telephony systems.
The latest technology is the APC connector. The end faces are still curved but are angled at an industry-standard eight degrees. This maintains a tight connection, and it reduces back reflection to about -70 dB. These connectors are preferred for CATV and analog systems.
PC and UPC connectors have reliable, low insertion losses. But their back reflection depends on the surface finish of the fiber. The finer the fiber grain structure, the lower the back reflection. And when PC and UPC connectors are continually mated and remated, back reflection degrades at a rate of about 4 to 6 dB every 100 matings for a PC connector. APC connector back reflection does not degrade with repeated matings. collapse
Black Box Explains... Speaker wire gauge.
Wire gauge (often shown as AWG, for American Wire Gauge) is a measure of the thickness of the wire. The more a wire is drawn or sized, the smaller its... more/see it nowdiameter will be. The lower the wire gauge, the thicker the wire.
For example, a 24 AWG wire is thinner than a 14 AWG wire. A lower AWG means longer transmission distance and better integrity. As a rule of thumb, power loss decreases as the wire size increases.
When it comes to choosing speaker cable, consider a few factors: distance, the type of system and amplifier you have, the frequencies of the signals being handled, and any specifications that the speaker manufacturer recommends.
For most home applications where you simply need to run cable from your stereo to speakers in the same room—or even behind the walls to other rooms—16 AWG cable is usually fine.
If youre considering runs of more than 40 feet (12.1 m), consider using 14 AWG or even 12 AWG cable. They both offer better transmission and less resistance over longer distances. You should probably choose 12 AWG cable for high-end audio systems with higher power output or for low-frequency subwoofers. As a rule of thumb, power loss decreases as the wire size increases.
To terminate your cable, choose gold connectors. Because gold resists oxidation over time, gold connectors wear better and offer better peformance than other connectors do. collapse
Black Box Explains...10-Gigabit Ethernet.
10-Gigabit Ethernet, sometimes called 10-GbE or 10 GigE, is the latest improvement on the Ethernet standard, ratified in 2003 for fiber as the 802.3ae standard, in 2004 for twinax cable... more/see it now
as the 802.3ak standard, and in 2006 for UTP as the 802.3an standard.
10-Gigabit Ethernet offers ten times the speed of Gigabit Ethernet. This extraordinary throughput plus compatibility with existing Ethernet standards has resulted in 10-Gigabit Ethernet quickly becoming the new standard for high-speed network backbones, largely supplanting older technologies such as ATM over SONET. 10-Gigabit Ethernet has even made inroads in the area of storage area networks (SAN) where Fibre Channel has long been the dominant standard. This new Ethernet standard offers a fast, simple, relatively inexpensive way to incorporate super high-speed links into your network.
Because 10-Gigabit Ethernet is simply an extension of the existing Ethernet standards family, it’s a true Ethernet standard—it’s totally backwards compatible and retains full compatibility with 10-/100-/1000-Mbps Ethernet. It has no impact on existing Ethernet nodes, enabling you to seamlessly upgrade your network with straightforward upgrade paths and scalability.
10-Gigabit Ethernet is less costly to install than older high-speed standards such as ATM.
And not only is it relatively inexpensive to install, but the cost of network maintenance and management also stays low—10-Gigabit Ethernet can easily be managed by local network administrators.
10-Gigabit Ethernet is also more efficient than other high-speed standards. Because it uses the same Ethernet frames as earlier Ethernet standards, it can be integrated into your network using switches rather than routers. Packets don’t need to be fragmented, reassembled, or translated for data to get through.
Unlike earlier Ethernet standards, which operate in half- or full-duplex, 10-Gigabit Ethernet operates in full-duplex only, eliminating collisions and abandoning the CSMA/CD protocol used to negotiate half-duplex links. It maintains MAC frame compatibility with earlier Ethernet standards with 64- to 1518-byte frame lengths. The 10-Gigabit standard does not support jumbo frames, although there are proprietary methods for accommodating them.
Fiber 10-Gigabit Ethernet standards
There are two groups of physical-layer (PHY) 10-Gigabit Ethernet standards for fiber:
LAN-PHY and WAN-PHY.
LAN-PHY is the most common group of standards. It’s used for simple switch and router
connections over privately owned fiber and uses a line rate of 10.3125 Gbps with 64B/66B
The other group of 10-Gigabit Ethernet standards, WAN-PHY, is used with SONET/SDH
interfaces for wide area networking across cities, states—even internationally.
10GBASE-SR (Short-Range) is a serial short-range fiber standard that operates over two multimode fibers. It has a range of 26 to 82 meters (85 to 269 ft.) over legacy 62.5-µm 850-nm fiber and up to 300 meters (984 ft.) over 50-µm 850-nm fiber.
10GBASE-LR (Long-Range) is a serial long-range 10-Gbps Ethernet standard that operates at ranges of up to 25 kilometers (15.5 mi.) on two 1310-nm single-mode fibers.
10GBASE-ER (Extended-Range) is similar to 10GBASE-LR but supports distances up to 40 kilometers (24.9 mi.) over two 1550-nm single-mode fibers.
10GBASE-LX4 uses Coarse-Wavelength Division Multiplexing (CWDM) to achieve ranges of 300 meters (984 ft.) over two legacy 850-nm multimode fibers or up to 10 kilometers (6.2 mi.) over two 1310-nm single-mode fibers. This standard multiplexes four data streams over four different wavelengths in the range of 1300 nm. Each wavelength carries 3.125 Gbps to achieve 10-Gigabit speed.
In fiber-based Gigabit Ethernet, the 10GBASE-SR, 10GBASE-LR, and 10GBASE-ER LAN-PHY standards have WAN-PHY equivalents called 10GBASE-SW, 10GBASE-LW, and 10GBASE-EW. There is no WAN-PHY standard corresponding to 10GBASE-LX4.
WAN-PHY standards are designed to operate across high-speed systems such as SONET and SDH. These systems are often telco operated and can be used to provide high-speed data delivery worldwide. WAN-PHY 10-Gigabit Ethernet operates within SDH and SONET using an SDH/SONET frame running at 9.953 Gbps without the need to directly map Ethernet frames into SDH/SONET.
WAN-PHY is transparent to data—from the user’s perspective it looks exactly the same as LAN-PHY.
10-Gigabit Ethernet over Copper
10GBASE-CX4 is a standard that enables Ethernet to run over CX4 cable, which consists of four twinaxial copper pairs bundled into a single cable. CX4 cable is also used in high-speed InfiniBand® and Fibre Channel storage applications.
Although CX4 cable is somewhat less expensive to install than fiber optic cable, it’s limited to distances of up to 15 meters. Because this standard uses such a specialized cable at short distances, 10GBASE-CX4 is generally used only in limited data center applications such as connecting servers or switches.
10GBASE-Kx is backplane 10-Gigabit Ethernet and consists of two standards. 10GBASE-KR is a serial standard compatible with 10GBASE-SR, 10GBASE-LR, and 10GBASE-ER. 10GBASE-KX4 is compatible with 10GBASE-LX4. These standards use up to 40 inches of copper printed circuit board with two connectors in place of cable. These very specialized standards are used primarily for switches, routers, and blade servers in data center applications.
10GBASE-T is the 10-Gigabit standard that uses the familiar shielded or unshielded copper UTP cable. It operates at distances of up to 55 meters (180 ft.) over existing Category 6 cabling or up to 100 meters (328 ft.) over augmented Category 6, or “6a,” cable, which is specially designed to reduce crosstalk between UTP cables. Category 6a cable is somewhat bulkier than Category 6 cable but retains the familiar RJ-45 connectors.
To send data at these extremely high speeds across four-pair UTP cable, 10GBASE-T uses sophisticated digital signal processing to suppress crosstalk between pairs and to remove signal reflections.
10-Gigabit Ethernet Applications
> 10-Gigabit Ethernet is already being deployed in applications requiring extremely
> As a lower-cost alternative to Fibre Channel in storage area networking (SAN)
> High-speed server interconnects in server clusters.
> Aggregation of Gigabit segments into 10-Gigabit Ethernet trunk lines.
> High-speed switch-to-switch links in data centers.
> Extremely long-distance Ethernet links over public SONET infrastructure.
Although 10-Gigabit Ethernet is currently being implemented only by extremely high-volume users such as enterprise networks, universities, telecommunications carriers, and Internet service providers, it’s probably only a matter of time before it’s delivering video to your desktop. Remember that only a few years ago, a mere 100-Mbps was impressive enough to be called “Fast Ethernet.”
Black Box Explains...Augmented Category 6 (CAT6A).
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... more/see it nowCAT6 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 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
There are two types of CAT6a cable, UTP and F/UTP.
Using optical break locators and OTDRs.
An optical time-domain reflectometer, or OTDR,
is an instrument used to analyze optical fiber. It sends a series of light pulses into the fiber under test and analyzes the light... more/see it nowthat is scattered and reflected back. These reflections are caused by faults such as breaks, splices, connectors, and adapters along the length of the fiber. The OTDR is able to estimate the overall length, attenuation or loss, and distance to faults. It’s also able to “see” past many of these “events” and display the results. The user is then able to see all the events along the length of the fiber run.
However, OTDRs do have a weakness?—?a blind spot that prevents them from seeing faults in the beginning of the fiber cable under test. To compensate for this, fiber launch boxes are used. Launch boxes come in predetermined lengths and connector types. These lengths of fiber enable you to compensate for this blind spot and analyze the length of fiber without missing any faults that may be in the first 10–30 meters of the cable.
An optical break locator, or OBL, is a simplified version of an OTDR. It’s able to detect high-loss events in the fiber such as breaks and determine the distance to the break. OBLs are much simpler to use than an OTDR and require no special training. However, there are limitations. They can only see to the first fault or event and do not display information on the portion of fiber after this event. 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 isnt limited to equipment from just one vendor when using an SNMP program. 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 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.
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 (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.
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.
USB 3.0: 4.8 Gbps
USB 2.0: 480 Mbps
USB 1.1: 12 Mbps
5 meters (3 meters for 3.0 devices requiring higher speeds).
Black Box Explains...Ceramic and composite ferrules.
Cables manufactured with ceramic ferrules are ideal for mission-critical applications or connections that are changed frequently. These cables are high quality and typically have a very long life. Ceramic ferrules... more/see it noware more precisely molded and fit closer to the fiber than their composite counterparts, which gives them a lower optical loss.
On the other hand, cables with composite ferrules are ideal for less critical applications or connections that won’t be changed frequently. Composite ferrule cables are characterized by low loss, good quality, and long life. collapse
Black Box Explains...Dry contacts.
A dry contact, also called a volt-free contact, is a relay contact that does not supply voltage. The relay energizes or de-energizes when a change to its input has occurred.... more/see it nowIn other words, a dry contact simply detects whether or not an input switch is open or closed.
The dry contacts in the ServSensor Contact provide a simple two-wire interface that can be easily adapted to third-party sensors and devices. Because you define what the open or closed condition means, dry contacts are infinitely adaptable.
Use dry contacts to monitor alarms such as fire alarms, burglar alarms, and alarms on power systems such as UPSs. A very common use for dry contacts is to detect whether a cabinet door is open or closed.