Black Box Explains...DDS vs. T1.
DDS (Digital Data Service) is an AT&T® service that transmits data digitally over dedicated leased lines. DDS lines use four wires, and support speeds up to 56 kbps; however, DDS... more/see it nowis actually a 64-kbps circuit with 8 kbps being used for signaling. You can also get 64-kbps (ClearChannel™) service. Since the transmission is digital, no modems are needed. Dedicated digital lines are ideal for point-to-point links in wide-area networks.
T1 is a dedicated transmission line operating at 1.544 Mbps. It’s comprised of 24 DSOs, each supporting speeds of 64 kbps. The user sends data at N x 56 or N x 64 over T1 circuits. T1 operates over twisted-pair cable and is suitable for voice, data, and image transmissions on long-distance networks. collapse
Black Box Explains... Local Multiplexors
Local multiplexors extend the distance between computers and terminals or printers that are connected via customer-installed or telco-supplied cable.
Like line drivers, local multiplexors extend RS-232 communications and must be... more/see it nowused in pairs. The difference between the two is that multiplexors merge several transmissions into one transmission over a single channel; line drivers generally transmit data over a single channel.
Local multiplexors operate over ordinary twisted-pair copper cable or fiber optic cable. Copper cable is typically used within buildings while fiber optic cable is the most common choice for connecting buildings in a campus environment. For in-building connections, copper cable is widely used because its comparatively inexpensive and easy to install. Your building might even have unshielded twisted-pair cable already in place.
The twisted-pair copper cable used for local multiplexors is run throughout buildings from the wallplates of each office or work area to a central wiring closet within the building. Wiring closets have centrally located punchdown blocks where all cables from the building are terminated. That way, when a connection needs to be changed or a new one needs to be made within the building, wiring can be easily rerouted on the punchdown blocks.
Selecting a local multiplexor.
When selecting a local multiplexor, keep in mind that copper-based multiplexors come in a vast array of types. Youll find multiplexors available with RJ-11, RJ-45, or terminal block connections for your in-house wiring and with RS-232 connections for your computer equipment. All these multiplexors can be used to link a local device to a remote device within a building. collapse
Black Box Explains...16850 UART.
The 16850 Universal Asynchronous Receiver/Transmitter (UART) features a 128-byte First In First Out (FIFO) buffer. When implemented with the appropriate onboard drivers and receivers, it enables your onboard serial ports... more/see it nowto achieve sustained data rates of up to 460.8 kbps.
The 16850 UART includes automatic handshaking (RTS/CTS) and automatic RS-485 line control. It also features external clocking for isochronous applications, a performance enhancement not offered by earlier UARTs. collapse
Black Box Explains...USB.
The Universal Serial Bus (USB) hardware (plug-and-play) standard makes connecting peripherals to your computer easy. USB 1.1, introduced in 1995, is the original USB standard. It has two data rates:... more/see it now12 Mbps and 1.5 Mbps.
USB 2.0, or Hi-Speed USB 2.0, was released in 2000. It increased the peripheral-to-PC speed from 12 Mbps to 480 Mbps, or 40 times faster than USB 1.1. This increase in bandwidth enabled the use of peripherals requiring higher throughput, such as CD/DVD burners, scanners, digital cameras, and video equipment. It is backward-compatible with USB 1.1.
The newest USB standard, USB 3.0 (or SuperSpeed USB), (2008) provides vast improvements over USB 2.0. It promises speeds up to
4.8 Gbps, nearly ten times that of USB 2.0.
USB 3.0 has the 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.
USB 3.0 adds a physical bus running in parallel with the existing 2.0 bus. 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 async, full-duplex data transfer instead of USB 2.0’s half-duplex polling method.
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. Also, USB 3.0 conserves more power when compared to USB 2.0, which uses power when the cable isn’t being used. collapse
Black Box Explains...Power problems.
The Threat — A sag is a decline in the voltage level. Also known as “brownouts,” sags are the most common power problem.
The Cause — Sags can be caused... more/see it nowlocally by the start-up demands of electrical devices such as motors, compressors, and elevators. Sags may also happen during periods of high electrical use, such as during a heat wave.
The Effect — Sags are often the cause of “unexplained” computer glitches such as system crashes, frozen keyboards, and data loss. Sags can also reduce the efficiency and lifespan of electrical motors.
The Threat — A blackout is a total loss of power.
The Cause — Blackouts are caused by excessive demand on the power grid, an act of nature such as lightning or an earthquake, or a human accident such as a car hitting a power pole or a backhoe digging in the wrong place.
The Effect — Of course a blackout brings everything to a complete stop. You also lose any unsaved data stored in RAM and may even lose the total contents of your hard drive.
The Threat — A spike, also called an impulse, is an instantaneous, dramatic increase in voltage.
The Cause — A spike is usually caused by a nearby lightning strike but may also occur when power is restored after a blackout.
The Effect — A spike can damage or completely destroy electrical components and also cause data loss.
The Threat — A surge is an increase in voltage lasting at least 1/120 of a second.
The Cause — When high-powered equipment such as an air conditioner is powered off, the excess voltage is dissipated though the power line causing a surge.
The Effect — Surges stress delicate electronic components causing them to wear out before their time.
The Threat — Electrical noise, more technically called electromagnetic interference (EMI) and radio frequency interference (RFI), interrupts the smooth sine wave expected from electrical power.
The Cause — Noise has many causes including nearby lightning, load switching, industrial equipment, and radio transmitters. It may be intermittent or chronic.
The Effect — Noise introduces errors into programs and data files. collapse
Black Box Explains...Code-operated and matrix switches.
Code-operated and matrix switches from Black Box give you computer-controlled switching for a variety of applications.
BLACK BOX® Code-Operated Switches enable one device to control up to 64 connected devices,... more/see it nowdepending on the code-operated switch. For instance, you can use one modem—not eight—to control eight devices. Code-operated switches are ideal for applications that require remote switching for file sharing or monitoring. Use code-operated switches for:
• Remote programming. Call in via remote sites to access servers, logic controllers, or any devices that require programming.
• Diagnostics. From your master control room, you can probe servers and run diagnostics.
Matrix switches enable more than one device to control other devices. Any port can connect to any port and perform more than one operation at a time independently. The code-operated switches talk to only one slave port at a time.
For instance, if your operation has four computers that need to share two printers and one modem, a matrix switch is what you need to handle the job. Use matrix switches for:
• Industrial applications. You can download instructions remotely to more than one programmable logic controller.
• Data sharing. PCs or industrial devices can be connected—locally or remotely—to other PCs and industrial devices or for file swapping. collapse
Black Box Explains...Terminal Servers
A terminal server (sometimes called a serial server) is a hardware device that enables you to connect serial devices across a network.
Terminal servers acquired their name because they were originally... more/see it nowused for long-distance connection of dumb terminals to large mainframe systems such as VAX™. Today, the name terminal server refers to a device that connects any serial device to a network, usually Ethernet. In this day of network-ready devices, terminal servers are not as common as they used to be, but they’re still frequently used for applications such as remote connection of PLCs, sensors, or automatic teller machines.
The primary advantage of terminal servers is that they save you the cost of running separate RS-232 devices. By using a network, you can connect serial devices even over very long distances—as far as your network stretches. It’s even possible to connect serial devices across the Internet. A terminal server connects the remote serial device to the network, and then another terminal server somewhere else on the network connects to the other serial device.
Terminal servers act as virtual serial ports by providing the appropriate connectors for serial data and also by grouping serial data in both directions into Ethernet TCP/IP packets. This conversion enables you to connect serial devices across Ethernet without the need for software changes.
Because terminal servers send data across a network, security is a consideration. If your network is isolated, you can get by with an inexpensive terminal server that has few or no security functions. If, however, you’re using a terminal server to make network connections across a network that’s also an Internet subnet, you should look for a terminal server that offers extensive security features. collapse
Black Box Explains... PCI buses
A Peripheral Component Interconnect (PCI) Bus enhances both speed and throughput. A PCI Local Bus is a high-performance bus that provides a processor-independent data path between the CPU and high-speed... more/see it nowperipherals. PCI is a robust interconnect interface designed specifically to accommodate multiple high-performance peripherals for graphics, full-motion video, SCSI, and LANs. collapse
Black Box Explains...DIN rail.
DIN rail is an industry-standard metal rail, usually installed inside an electrical enclosure, which serves as a mount for small electrical devices specially designed for use with DIN rails. These... more/see it nowdevices snap right onto the rails, sometimes requiring a set screw, and are then wired together.
Many different devices are available for mounting on DIN rails: terminal blocks, interface converters, media converter switches, repeaters, surge protectors, PLCs, fuses, or power supplies, just to name a few.
DIN rails are a space-saving way to accommodate components. And because DIN rail devices are so easy to install, replace, maintain, and inspect, this is an exceptionally convenient system that has become very popular in recent years.
A standard DIN rail is 35 mm wide with raised-lip edges, its dimensions outlined by the Deutsche Institut für Normung, a German standardization body. Rails are generally available in aluminum or steel and may be cut for installation. Depending on the requirements of the mounted components, the rail may need to be grounded. collapse
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