Advanced Configuration and Power Interface
ACPI (Advanced Configuration and Power Interface) is an industry specification for the efficient handling of power consumption in desktop and mobile computers. ACPI specifies how a computer’s basic input/output system, operating system, and peripheral devices communicate with each other about power usage.
With ACPI, the following capabilities are possible (assuming the operating system supports them):
• The user can specify at what time a device, such as a display monitor, is to turn off or on.
• The user of a notebook computer can specify a lower-level of power consumption when the battery starts running low so that essential applications can still be used while other, less important applications are allowed to become inactive.
• The operating system can lower the clock speed during times when applications don’t require the full processor clock speed.
• The operating system can reduce motherboard and peripheral device power needs by not activating devices until they are needed.
• The computer can enter a stand-by mode when no one is using it, but with modem power left on to receive incoming faxes.
• Devices can be plug and play. As soon as plugged in, they can be controlled by ACPI.
ACPI must be supported by the computer motherboard, basic input/output system (BIOS), and the operating system. One of several power schemes can be chosen. Within a power scheme, the user can control the power to individual devices. In order for ACPI to work on your computer, your BIOS must include the ACPI software and the operating system must be ACPI-compatible. ACPI is designed to work with Windows 98 and with Windows 2000. If you have Windows 98, you’ll find a description of ACPI in the help files. Click Start->Help->Index-> and type in: ACPI.
ACPI is in part a response to global concerns about energy conservation and environmental control. ACPI replaces Intel’s SL technology and the more recent APM (Advanced Power Management) technology. Based on the collaborative effort of Intel, Toshiba, and Microsoft, ACPI moves away from power management that simply times out during inactivity to a more sophisticated demand-based power management. ACPI components collect information about power consumption from the computer and gives that information to the operating system. The operating system then distributes power to the different computer components on an as-needed basis. With ACPI, the computer can power itself down to a deep sleep state but still be capable of responding to an incoming phone call or a timed backup procedure. Another feature of ACPI is the "hibernation" mode. Before the computer goes into a deep sleep or hibernation, the contents of RAM are written to an image file and saved on the hard drive. When the computer is turned back on, the image file is reloaded, eliminating the need to reboot the system and open applications.
Advanced Encryption Standard
The Advanced Encryption Standard (AES) is an encryption algorithm for securing sensitive but unclassified material by US Government agencies and, as a likely consequence, may eventually become the de facto encryption standard for commercial transactions in the private sector. (Encryption for the US military and other classified communications is handled by separate, secret algorithms.)
In January 1997, a process was initiated by the National Institute of Standards and Technology (NIST), a unit of the US Commerce Department, to find a more robust replacement for the Data Encryption Standard (DES) and to a lesser degree Triple DES. The specification called for a symmetric algorithm (same key for encryption and decryption) using block encryption (see block cipher) of 128 bits in size, supporting key sizes of 128,192 and 256 bits, as a minimum. The algorithm was required to be royalty-free for use worldwide and offer security of a sufficient level to protect data for the next 20 to 30 years. It was to be easy to implement in hardware and software, as well as in restricted environments (for example, in a smart card) and offer good defenses against various attack techniques.
The entire selection process was fully open to public scrutiny and comment, it being decided that full visibility would ensure the best possible analysis of the designs. In 1998, the NIST selected 15 candidates for the AES, which were then subject to preliminary analysis by the world cryptographic community, including the National Security Agency. On the basis of this, in August 1999, NIST selected five algorithms for more extensive analysis. These were:
• MARS, submitted by a large team from IBM Research
• RC6, submitted by RSA Security
• Rijndael, submitted by two Belgian cryptographers, Joan Daemen and Vincent Rijmen
• Serpent, submitted by Ross Andersen, Eli Biham and Lars Knudsen
• Twofish, submitted by a large team of researchers including Counterpane’s respected cryptographer, Bruce Schneier
Implementations of all of the above were tested extensively in ANSI C and Java languages for speed and reliability in such measures as encryption and decryption speeds, key and algorithm set-up time and resistance to various attacks, both in hardware- and software-centric systems. Once again, detailed analysis was provided by the global cryptographic community (including some teams trying to break their own submissions). The end result was that on October 2, 2000, NIST announced that Rijndael had been selected as the proposed candidate as the AES. After a 90 day period of public comment when the algorithm is presented as a Federal Information Processing Standard (FIPS), the Secretary of Commerce will approve it after final, detailed analysis. Final, official acceptance is expected some time in June 2001.
Advanced Function Printing
Advanced Function Printing (AFP) is an IBM architecture and family of associated printer software and hardware that provides document and information presentation control independent of specific applications and devices. Using AFP, users can control formatting, the form of paper output, whether a document is to be printed or viewed online, and manage document storage and access in a distributed network across multiple operating system platforms. AFP is primarily used in large enterprises with printer rooms and expensive high-speed printers. AFP applications allow users or print room operators to distributed print jobs among a group of printers and to designate backup printers when one fails. IBM considers AFP to be a "cornerstone" of EDM applications such as print-and-view, archive and retrieval, and Computer Output to Laser Disk (COLD).
AFP printer and software support is provided in all of IBM’s major operating systems: OS/390, virtual machine, VSE, OS/ 400, AIX, and OS/2, as well as in DOS and Windows.
The AFP architecture is primarily designed to work with the Intelligent Printer Datastream (IPDS), but also can print using Hewlett-Packard’s Printer Control Language (PCL) and the Page Printer Datastream(PPDS). Other supported data streams include ASCII, Metafiles, Postscript, TeX, and Ditroff.
An application program interface (API) is provided so that COBOL application programmers can use AFP functions without having to specify them using AFP syntax or semantics.
Advanced Intelligent Network
The Advanced Intelligent Network (AIN) is a telephone network architecture that separates service logic from switching equipment, allowing new services to be added without having to redesign switches to support new services. It encourages competition among service providers since it makes it easier for a provider to add services and it offers customers more service choices. Developed by Bell Communications Research, AIN is recognized as an industry standard in North America. Its initial version, AIN Release 1, is considered a model toward which services will evolve. Meanwhile, evolutionary subsets of AIN Release 1 have been developed. These are shown in the (#ainrels) AIN Release Table below. Elsewhere, the International Telecommunications Union (see ITU-TS), endorsing the concepts of AIN, developed an equivalent version of AIN called Capability Set 1 (CS-1). It comes in evolutionary subsets called the Core INAP capabilities.
How It Works
Briefly, here’s how AIN Release 1 works:
• A telephone caller dials a number that is received by a switch at the telephone company central office.
• The switch—known as the Service Switching Point (SSP)—forwards the call over a Signaling System 7 (SS7) network to a Service Control Point (SCP) where the service logic is located.
• The Service Control Point identifies the service requested from part of the number that was dialed and returns information about how to handle the call to the Service Switching Point. Examples of services that the SCP might provide include area number calling service, disaster recovery service, do not disturb service, and 5-digit extension dialing service.
• In some cases, the call can be handled more quickly by an Intelligent Peripheral (IP) that is attached to the Service Switching Point over a high-speed connection. For example, a customized voice announcement can be delivered in response to the dialed number or a voice call can be analyzed and recognized.
• In addition, an "adjunct" facility can be added directly to the Service Switching Point for high-speed connection to additional, undefined services.
One of the services that AIN makes possible is Local Number Portability (Local Number Portability).
The AIN Release Table
|
AIN Release Release 0 |
Capabilities Trigger checkpoints at off-hook, digit collection and analysis, and routing points of call Code gapping to check for overload conditions at SCP 75 announcements at the switching system Based on ANSI TCAP issue 1 |
|
Release 0.1 |
Adds a formal call model that distinguishes the originating half of the call from the terminating half Additional triggers 254 announcements at the switching system Based on ANSI TCAP issue 2 |
|
Release 0.2 Release 1 |
Adds Phase 2 Personal Communication Service (PCS) support Voice Activated Dialing (VAD) ISDN-based SSP-IP interface Busy and no-answer triggers Next events list processing at SCP Default routing A full set of capabilities |
Advanced Mobile Phone Service
Advanced Mobile Phone Service (AMPS) is a standard system for analog signal cellular telephone service in the United States and is also used in other countries. It is based on the initial electromagnetic radiation spectrum allocation for cellular service by the Federal Communications Commission (FCC) in 1970. Introduced by AT&T in 1983, AMPS became and currently still is the most widely deployed cellular system in the United States.
AMPS allocates frequency ranges within the 800 and 900 megahertz (MHz) spectrum to cellular telephone. Each service provider can use half of the 824-849 MHz range for receiving signals from cellular phones and half the 869-894 MHz range for transmitting to cellular phones. The bands are divided into 30 kHz sub-bands, called channels. The receiving channels are called reverse channels and the sending channels are called forward channels. The division of the spectrum into sub-band channels is achieved by using frequency division multiple access (FDMA).
The signals received from a transmitter cover an area called a cell. As a user moves out of the cell’s area into an adjacent cell, the user begins to pick up the new cell’s signals without any noticeable transition. The signals in the adjacent cell are sent and received on different channels than the previous cell’s signals to so that the signals don’t interfere with each other.
The analog service of AMPS has been updated with digital cellular service by adding to FDMA a further subdivision of each channel using time division multiple access (TDMA). This service is known as digital AMPS (D-AMPS). Although AMPS and D-AMPS originated for the North American cellular telephone market, they are now used worldwide with over 74 million subscribers, according to Ericsson, one of the major cellular phone manufacturers.
Advanced Peer-to-Peer Networking (APPN)
Advanced Peer-to-Peer Networking (APPN), part of IBM’s Systems Network Architecture (SNA), is a group of protocols for setting up or configuring program-to-program communication within an IBM SNA network. Using APPN, a group of computers can be automatically configured by one of the computers acting as a network controller so that peer programs in various computers will be able to communicate with other using specified network routing. APPN features include:
• Better distributed network control; because the organization is peer-to-peer rather than solely hierarchical, terminal failures can be isolated
• Dynamic peer-to-peer exchange of information about network topology, which enables easier connections, reconfigurations, and routing
• Dynamic definition of available network resources
• Automation of resouce registration and directory lookup
• Flexibility, which allows APPN to be used in any type of network topology
How Dynamic Configuration Works
APPN works with Advanced Program-to-Program Communication (APPC) software that defines how programs will communicate with each other through two interfaces: one that responds to requests from application programs that want to communicate and one that exchanges information with communications hardware. When one program wants to communicate with another, it sends out a request (called an allocate call) that includes the destination’s logical unit (LU) name—the APPC program on each computer that uniquely identifies it. APPC sets up a session between the originating and destination LUs.
APPN network nodes are differentiated as low entry networking (LEN) nodes, end nodes (ENs), and network nodes (NNs). When the network computers are powered on and the software activated, links are established throughout the specified topology. The linked nodes exchange information automatically. If we consider a simplified APPN network, with one end node connected to a network node, the following would describe the sequence of events:
• Each node indicates APPN capability and defines its node type.
• The network node asks the end node if it requires a network node server, which handles requests for LU locations.
• If it responds that it does, the two nodes establish APPC sessions to exchange program-to-program information.
• The end node registers any other LUs defined at its node by sending the networked node formatted information gathered from the APPC session.
• After this sequence is completed, the network node knows the location of the EN and what LUs are located there. This information, multiplied across the network, enables LU location and routing.
Advanced Television Enhancement Forum
The Advanced Television Enhancement Forum (ATVEF) is an alliance of leaders in the broadcast and cable industry, the consumer electronics industry, and the computer industry that developed the ATVEF enhanced content specification. The ATVEF specification delivers Web content to television viewers using current Internet technologies over both analog and digital television (DTV) systems. ATVEF uses existing terrestrial, cable, satellite, and Internet networks to deliver Web content. ATVEF content is broadcast over one-way or two-way television systems. Supported files include Hypertext Markup Language (HTML), Virtual Reality Modeling Language (VRML), Java, and private data files. Consumers can receive Web content using a personal computer, cable or satellite set-top box, or WebTV device. The ATVEF specification consists of three parts: the announcement, trigger, and content:
• The announcement notifies the television viewer of any current Web content available and expires after a set time period. The announcement also includes information that helps the set-top box to decide whether to accept the Web content or to determine whether the Web content is designed to automatically begin without authorization.
• The trigger contains the URL that points to the Web content.
• The content delivered is a collection of Web pages that is displayed along with the television program. It can include text, pictures, and audio files. If the television system is a two-way system, the viewer can browse Web pages and even purchase advertised items using his television.
The ATVEF specification also defines a degree of forward error correction. The data to be transmitted is processed through an algorithm that adds extra bits for error correction. If the Web content is damaged during transmission, the extra bits are used to correct the damage. It also allows the data to be reconstructed if received out of order. The forward error correction defined by the ATVEF specification also allows a viewer to receive Web content even if the viewer has tuned into the middle of a broadcast.
Advanced Television Systems Committee
The Advanced Television Systems Committee (ATSC) is a standards organization that was created in 1982 as part of the Advanced Television Committee (ATV) to promote the establishment of technical standards for all aspects of advanced television systems. Based in Washington, D.C., ATSC has grown from 25 original organizational members to an international membership of over 200, including broadcasters, motion picture companies, telecommunications carriers, cable TV programmers, consumer electronics manufacturers, and computer hardware and software companies.
The ATSC developed standards for digital television (DTV) that specify technologies for the transport, format, compression, and transmission of DTV in the U.S. ATSC DTV Standards developed, or in development currently, include digital high definition television (term>>HDTV), standard definition television (SDTV), datacasting (the transmission of separate information streams that might allow, for example, someone watching a baseball game to choose a different camera angle, or someone watching a cooking show to view and download particular recipes), multichannel surround-sound audio, conditional access (methods, such as encryption or electronic locking systems, used to restrict service access to authorized users), and interactive services. For SDTV and HDTV, ATSC chose MPEG-2 for video and Dolby Digital for audio.
ATSC standards are expected to revolutionize the television industry as defined by the National Television Standards Committee (NTSC) standards set in 1953. ATSC standards for DTV are being adopted internationally.
AES/EBU
AES/EBU (Audio Engineering Society/European Broadcasting Union) is the name of a digital audio transfer standard. The AES and EBU developed the specifications for the standard.
The AES/EBU digital interface is usually implemented using 3-pin XLR connectors, the same type connector used in a professional microphone. One cable carries both left-and right-channel audio data to the receiving device. AES/ EBU is an alternative to the S/PDIF standard.
AF
AF (audio frequency) (also abbreviated af or a.f.) refers to alternating current (AC) having a frequency such that, if applied to a transducer such as a loudspeaker or headset, it will produce acoustic waves within the range of human hearing. The AF range is generally considered to be from 20 Hz to 20,000 Hz.
All telephone circuits operate with AF signals in a restricted range of approximately 200 Hz to 3000 Hz. A telephone-line modem is an AF device that converts binary digital data into analog signals that can be transmitted over the telephone circuit, and also converts incoming AF signals into binary digital data.
