| Term |
Definition |
| A and B Signaling |
A technique used in T1 (1.544 million bit per second digital) transmission systems to carry dial and control information within selected transmission frames. Bits are "robbed" from each of the sub-channels to provide this facility. |
| A/D converter |
Analog-to-Digital converter. A circuit board or integrated circuit that converts analog input signals to digital equivalent-weight output signals. |
| AAL Connection |
An association established by the AAL between two or more next higher layer entities. |
| AAL0 (ATM Adaption Layer 0) |
AAL0 is a straight packaging of 48 bytes of data within an ATM cell. AAL0 is often used to carry signaling ATM cells, which are treated in this device as "raw cells". |
| AAL5 (ATM Adaption Layer 5) |
AAL5 is a protocol used to carry higher-layer datagrams while enhancing the link layer with services available through ATM. Defined in the ITU standard I.363.5, AAL5 is typically used to carry IP datagrams over ATM, but can be used for other higher-layer. |
| AAL-1 (ATM Adaptation Layer Type 1) |
AAL functions in support of constant bit rate, time-dependent traffic such as voice and video. |
| AAL-3/4 (ATM Adaptation Layer Type 3/4) |
AAL functions in support of variable bit rate, delay-tolerant data traffic requiring some sequencing and/or error detection support. Originally two AAL types, i.e. connection-oriented and connectionless, which have been combined. |
| Abbreviated Address Calling |
A calling method which allows the user to employ an address having fewer characters that the destination's assigned device address when initiating a connection. May also be called abbreviated dialing when specifically used in connection with telephone systems. |
| Abbreviated dialing |
A feature on wireless phones where you enter just one or two digits from the keypad and then initiate the call. The phone searches its speed dial directory and associates the entire number with the two-digit speed dial position you've entered. |
| ABI |
Application Binary Interface - Specification for hardware platform and operating system. |
| ABR |
AutoBaud Rate detect. |
| AC |
Alternating Current. |
| AC Coupled |
AC coupling passes a signal through a capacitor to remove any DC offset, or the overall voltage level that the video signal "rides" on. One way to find the signal is to remove the DC offset by AC coupling, and then do DC restoration to add a known DC offset (one that we selected). Another reason AC coupling is important is that it can remove large (and harmful) DC offsets. |
| AC-3 |
An early name for Dolby Digital. |
| Acceptance Angle |
The range of an angle measured from the axis of the fiber over which light is optimally accepted from one core to another. |
| Acceptance Pattern |
This is the curve over a range of launch angles showing the amount of power transmitted as a function of those angles. In this case one could characterize the actual fiber angle and geometry of core terminations to find the optimal angle. |
| Acceptor |
The Bluetooth device receiving an action from another Bluetooth device. The device sending the action is called the initiator. The acceptor is typically part of an established link. |
| Access Line |
The physical telecommunications circuit connecting an end-user location with the serving central office in a local network environment. Also called the local loop or "last mile." |
| Access Network |
A "sub-network" which is implemented to provide simple access to a more complex network. The access network often allows communication between a limited, local, group of users and also additional access to a wider area population. |
| Access Nodes |
Points on the edge of the access network that concentrate individual access lines into a smaller number of feeder lines. Access Nodes may also perform various forms of protocol conversion. Typical Access Nodes are Digital Loop Carrier systems concentrating individual voice lines to T1 lines, cellular antenna sites, PBXs, and Optical Network Units (ONUs). |
| Access Rate |
The transmission speed of the physical access circuit between the end user location and the local network. This is generally measured in bits per second. Also called Access Speed. |
| Access Routines |
Specific software routines that provide access to network resources. |
| Accumulator |
A special register, or memory location, in the arithmetic and logic unit of the computer processor. It is used to hold the result of a calculation temporarily or to store data that is being transferred. |
| ACCUNET |
A 1.5 million bit per sec (T1) digital transmission, packet switched, network service offered by AT&T. |
| ACCY |
Accessory. |
| ACD |
Automatic Call Distribution - Routing of an incoming telephone call to next available operator. |
| ACE |
Advanced Computing Environment - Open standard based on UNIX and Windows NT. |
| ACIA |
Asynchronous Communication Interface Adapter. |
| ACL |
Asynchronous Connectionless Link. An Asynchronous (packet-switched) connection between two devices created on the LMP level. This type of link is used primarily to transmit ACL packet data. |
| ACM |
Association for Computing Machinery. |
| ACO |
Authenticated Ciphering Offset. |
| Acoustic Coupler |
A type of modem which generates audible tones so that computer based data can be transferred into a transmission medium using a standard telephone hand-set. |
| Acoustic Delay Line |
A line which, by design, delays audio signals by recirculating them in some type of medium. May also be called a sonic delay line. |
| ACP |
Audio Control Panel. |
| ACPI |
Advanced Configuration Power Interface. |
| ACPR |
Adjacent Channel Power Ratio. |
| Active Coupler |
A coupler that includes a receiver and one or more transmitters. The idea is to regenerate the input signal and then send them on. |
| ACTS |
Advanced Communications Technologies and Services. |
| Adaptive Differential PCM (ADPCM) |
ADPCM is a compression standard that allows the encoding of PCM data at rates of 40, 32, 24 and 16 kbps. Defined by the ITU standard G.726. ADPCM running at 32 kbps is often used as the definition of "toll" quality, or quality that is comparable or superior to that of the PSTN today. |
| Adaptive Routing |
A routing (switching) method which can automatically adapt to changes in the transmission facilities available within a network. This type of routing may, in a simple form, only accommodate failed lines or failed switching nodes. In a more complex form varying traffic loads may also be accommodated. |
| ADC |
Analog-to-Digital Converter. |
| Add/Drop Devices and Multiplexing |
The ability to add or drop specific portions of a signal from a stream without multiplexing or demultiplexing the entire signal. |
| Addressable Resolution |
The highest resolution signal that a display device (TV or monitor) can accept. The device, however, may not be capable of displaying this resolution. |
| ADLC |
Advanced Data Link Controller. |
| ADSL |
ADSL (Asymmetric digital subscriber line) is a technology for transmitting digital information at high bandwidths on existing phone lines to homes and businesses. ADSL is asymmetric in that it uses most of the channel to transmit downstream to the user and only a small part to receive information from the user. ADSL was specifically designed to exploit the one-way nature of most multimedia communication in that large amounts of information flow toward the end user and only a small amount of interactive control information is returned. |
| ADT |
Asynchronous Data Transfer - Transmission technique used in ISDN PBXs to allocate bandwidth. |
| Advanced Branch Exchange |
A private branch exchange with advanced features normally including the ability to handle both voice and data in an integrated manner. |
| AF |
Audio Frequency. |
| AFC |
Automatic Frequency Control. |
| AG |
Audio Gateway. |
| AGC |
Automatic Gain Control. |
| Aged Packet |
A data packet which has exceeded it's maximum node visit count or time in the network limit. |
| AGP |
Accelerated Graphics Port. |
| AI |
Amplitude Imbalance. |
| AIM |
Apple/IBM/Motorola. |
| Airline Control Protocol |
Data link layer polled protocol that runs in full-duplex mode over synchronous serial (V.24) lines and uses the binary-coded decimal (BCD) character set. |
| Airtime |
Actual time spent using a wireless phone. |
| A-Law |
Companding/encoding law commonly used in Europe. |
| A-Law/or µ-Law Companding |
8 bit PCM Binary code. The codes are used almost universally for PCM digital switching and transmission. When a reference is made to PCM it is these codes which are being referred to (A-Law version in Europe and µ-Law version in North America). |
| ALC |
Automatic Level Control. |
| Aliasing Noise |
A distortion component created when a sampled signal bandwidth is effectively greater than 1/2 the sample rate. |
| Allocation Access |
A network access method whereby devices are allocated time on a transmission medium. The most popular LAN method is implemented by the use of a token and is used in the IEEE 802.4 and IEEE 802.5 LAN specifications. |
| Alpha Mix |
This is a way of combining two images. How the mixing is performed is provided by the alpha channel. The little box that appears over the left-hand shoulder of a news anchor is put there by an alpha mixer. Wherever the little box is to appear, a "1" is put in the alpha channel. Wherever it doesn't appear, a "0" is used. When the alpha mixer sees a "1" coming from the alpha channel, it displays the little box. Whenever it sees a "0", it displays the news anchor. Of course, it doesn't matter if a "1" or a "0" is used, but you get the point. |
| Alternate-Mark Inversion Signal (AMI) |
A pseudo-ternary signal, conveying binary digits, in which succes-sive 'marks' are normally of alternate, positive and negative, polarity but equal in amplitude. A 'space' is of zero amplitude. |
| ALU |
Arithmetic Logic Unit. |
| AM |
Amplitude Modulation; also Active Matrix. |
| AM_ADDR |
Active Member Address. |
| AMA |
American Electronics Association. |
| Amplified Spontaneous Emissions (ASE) |
Noise that is added to an optical signal when it is amplified. This noise (or ASE) accumulates and builds in optical spans that have multiple optical amplifiers between regenerators. |
| Amplifier |
A device which increases the strength of an analog signal without changing it's form and information content. |
| Amplitude Modulation |
The process whereby the amplitude (or strength) of an analog signal is varied to carry digital information. A popular method used in low cost modems. |
| AMPS (Advanced Mobile Phone Service) |
The analog cellular mobile phone system in North and South America and more than 35 other countries. It uses the FDMA transmission technology. AMPS is the cellular equivalent of POTS. |
| ANA |
Article Numbering Association. |
| Analog |
A transmission method using continuous electrical signals, varying in amplitude or frequency in response to changes of sound, light, position, etc. impressed on a transducer in the sending unit. |
| Analog Loopback |
A technique for testing transmission equipment and devices that isolates faults to the analog receiving or transmitting circuitry. |
| Analog Signal |
Continuously varying with an amplitude which is an analog of the original information, and thus may have virtually n infinite numbers of states. Contrasted with a digital signal which has only a very limited number of discrete states. |
| Analog TV |
Standard television broadcasts analog TV. Analog signals vary continuously, representing fluctuations in color and brightness. |
| Angled End |
A fiber whose end is polished with purpose to an angle to reduce reflectance. |
| Angular Misalignment Loss |
This is the loss of optical power due to an angular deviation from the optimal angle and alignment between the source to another fiber, or to a detector for instance. |
| ANI |
Automatic Number Identification. |
| Anisochronous Transmission |
A transmission process in which there is always an integral unit of intervals between any two significant instants in the same group. A group may be a character or a block of characters. |
| ANR |
Active Noise Reduction. |
| ANSI |
American National Standards Institute. |
| Anti-Aliasing Filter |
A filter (normally low pass) which band limits the input signal before sampling, to less than half the sampling rate, to prevent aliasing noise. |
| Aperture Delay |
Aperture delay is the time from an edge of the input clock of the ADC until the time the ADC actually takes the sample. The smaller this number, the better. |
| Aperture Jitter |
The uncertainty in the aperture delay. This means the aperture delay time changes a little bit each time, and that little bit of change is the aperture jitter. |
| Application data |
The "data" unit carried by the transport layer. This will typically be the UDP payload in a voice-over-IP implementation, though it could be TCP payload or others for other applications. |
| AR (Access Rate) |
The data rate of the user access channel in a Frame Relay network. The speed of the access channel determines how fast (maximum rate) the end user can inject data into a Frame Relay network. |
| ARB |
Arbitrary waveform generator. |
| ARP (Address Resolution Protocol) |
A protocol designed for Ethernet that allows the MAC address associated to a network address (usually an IP address) to be known so the packet can be sent over Ethernet. Defined by IETF RFC826 & STD37. |
| ASA |
American Standards Association. |
| ASIC |
Application Specific Integrated Circuit. |
| ASK |
Amplitude Shift Keying. |
| ASP |
Analog signal processor. |
| Aspect Ratio |
Refers to the width of a picture relative to its height. If an NTSC picture is 4 feet wide, it will be 3 feet high; thus it has a 4:3 aspect ratio. HDTV has a 16:9 aspect ratio. |
| ASRP |
Application Specific RISC Processor. |
| ASSP |
Application Specific RISC Processor. |
| Asynchronous Transfer Mode (ATM) |
Cell switched technology. Uses 53 byte cells to transmit information (Voice or Data) across the ATM network. |
| ATM Address |
Defined in the UNI Specification as 3 formats, each having 20 bytes in length. |
| ATM-ARP |
ATM Address Resolution Protocol - An address resolution protocol for mapping ATM and IP addresses (each host is assigned a unique IP address). It can be used for discovering LAN hosts attached to an ATM network or in classical IP over ATM. |
| ATM-SAP |
ATM Service Access Point - The physical interface at the boundary between the AAL and the ATM layer. |
| AToMMIB |
ATM MIB. IETF-defined Management Information Base (MIB) for managing VP/VC links and ATM PVC supported interfaces and services. |
| ATRAC |
Adaptive Transform Acoustic Coding. |
| ATSC |
Advanced Television Systems Committee. They defined the SDTV and HDTV standards for the United States, using MPEG 2 for video and Dolby Digital for audio. Other countries are also adopting the ATSC HDTV standard. |
| Attenuation |
The loss of energy (strength) of a signal as it passes through a transmission medium. The energy loss is the result of the electrical resistance offered by the specific medium. |
| Audio Frequency |
The range of frequencies which are detectable by the human ear. |
| Audio Modulation |
Refers to modifying an audio subcarrier with audio information so that it may be mixed with the video information and transmitted. |
| Audio Subcarrier |
A specific frequency that is modulated with audio data. |
| AUSTPAC |
A packet switched network implemented in Australia. |
| AUTODIN |
AUTOmatic Digital Network. |
| AUX |
Auxiliary. |
| AV |
Audio/Visual. |
| AVD |
Alternate voice/data. |
| AVI |
Audio Video Interleaved. |
| AWG |
The American Wire Gauge System, which specifies wire width. |
| AWGN |
Additive white gaussian noise. |
