- Industry: Telecommunications
- Number of terms: 29235
- Number of blossaries: 0
- Company Profile:
ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven standards for the information, entertainment and communications industry.
An abbreviation for the ASCII transmission-control character meaning "Transmitter off. "
Industry:Telecommunications
An abbreviation for the ASCII transmission-control character meaning "Transmitter on. "
Industry:Telecommunications
An abnormally high ionization density in the D region caused by an occasional sudden solar flare, i.e., outburst of ultraviolet light from the Sun. Note: The SID results in a sudden increase in radio-wave absorption that is most severe in the upper medium-frequency (MF) and lower high-frequency (HF) ranges.
Industry:Telecommunications
An abrupt change of the center wavelength of a laser, caused by laser instability.
Industry:Telecommunications
An absorber of energy. 2. In communications, a device that receives information, control, or other signals from a source. 3. A location at which a specified multiplex structure is terminated through connected equipment removing the frame alignment signal and disassembling the channel time slots.
Industry:Telecommunications
An abstract description of the digital communications between application processes running in distinct systems. The model employs a hierarchical structure of seven layers. Each layer performs value-added service at the request of the adjacent higher layer and, in turn, requests more basic services from the adjacent lower layer: Physical Layer: Layer 1. The lowest of seven hierarchical layers. The Physical layer performs services requested by the Data Link Layer. The major functions and services performed by the physical layer are: (a) establishment and termination of a connection to a communications medium; (b) participation in the process whereby the communication resources are effectively shared among multiple users, e.g., contention resolution and flow control; and, (c) conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel. Data Link Layer: Layer 2. This layer responds to service requests from the Network Layer and issues service requests to the Physical Layer. The Data Link Layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical Layer. Note: Examples of data link protocols are HDLC and ADCCP for point-to-point or packet-switched networks and LLC for local area networks. Network Layer: Layer 3. This layer responds to service requests from the Transport Layer and issues service requests to the Data Link Layer. The Network Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks while maintaining the quality of service requested by the Transport Layer. The Network Layer performs network routing, flow control, segmentation/desegmentation, and error control functions. Transport Layer: Layer 4. This layer responds to service requests from the Session Layer and issues service requests to the Network Layer. The purpose of the Transport Layer is to provide transparent transfer of data between end users, thus relieving the upper layers from any concern with providing reliable and cost-effective data transfer. Session Layer: Layer 5. This layer responds to service requests from the Presentation Layer and issues service requests to the Transport Layer. The Session Layer provides the mechanism for managing the dialogue between end-user application processes. It provides for either duplex or half-duplex operation and establishes checkpointing, adjournment, termination, and restart procedures. Presentation Layer: Layer 6. This layer responds to service requests from the Application Layer and issues service requests to the Session Layer. The Presentation Layer relieves the Application Layer of concern regarding syntactical differences in data representation within the end-user systems. Note: An example of a presentation service would be the conversion of an EBCDIC-coded text file to an ASCII-coded file. Application Layer: Layer 7, the highest layer. This layer interfaces directly to and performs common application services for the application processes; it also issues requests to the Presentation Layer. The common application services provide semantic conversion between associated application processes. Note: Examples of common application services of general interest include the virtual file, virtual terminal, and job transfer and manipulation protocols.
Industry:Telecommunications
An abstract, implementation-independent, interaction between a layer service user and a layer service provider.
Industry:Telecommunications
An access control concept utilizing an abstract machine to mediate all access to objects by subjects.
Industry:Telecommunications
An access line (e.g., for WATS or TWX service) between a subscriber's premises in one toll rate center and a serving central office located in a different toll rate center.
Industry:Telecommunications
An access line composed of digital facilities, containing no analog sections, and having a digital interface at the local digital exchange office (DEO) and a digital interface at the end-user voice terminal, voiceband data terminal, PBX, or interconnecting network.
Industry:Telecommunications
