Communication Definitions
"A" to Asc, "Asy" to "Bc", "Be" to "Bi",
"Bl" to "Cz", "D" to "E", "F" to "L",
"M" to "Mod", "Mu" to "Nu", "O" to "Z"

Open Systems Interconnection (OSI) Protocol Specification: The lowest level of abstraction within the OSI standards scheme. Note: Each OSI Protocol Specification operates at a single layer. Each defines the primitive operations and permissible responses required to exchange information between peer processes in communicating systems to carry out all or a subset of the services defined within the OSI Service Definitions for that layer. Protocol Definitions

Packet switching: The process of routing and transferring data by means of addressed packets so that a channel is occupied during the transmission of the packet only, and upon completion of the transmission the channel is made available for the transfer of other traffic.

Physical topology: The physical configuration, i.e., interconnection, of network elements, e.g., cable paths, switches, concentrators. Note: Physical topology is in contrast to logical topology. For example, a logical loop may consist of a physical star configuration, or a physical loop. Also see Bus Topologies.

Network Interface Topologies

Plesiochronous: That relationship between two signals such that their corresponding significant instants occur at nominally the same rate, any variations being constrained within a specified limit. Note: There is no limit to the phase difference that can accumulate between corresponding significant instants over a long period of time.

Protocol: A formal set of conventions governing the format and control of interaction among communicating functional units. Note: Protocols may govern portions of a network, types of service, or administrative procedures. For example, a data link protocol is the specification of methods whereby data communications over a data link are performed in terms of the particular transmission mode, control procedures, and recovery procedures. In layered communications system architecture, a formal set of procedures that are adopted to facilitate functional inter-operation within the layered hierarchy. [Protocols]

Serial: Pertaining to a process in which all events occur one after the other; for example, the serial transmission of the bits of a character according to the CCITT V.25 protocol. Pertaining to the sequential or consecutive occurrence of two or more related activities in a single device or channel. 3. Pertaining to the sequential processing of the individual parts of a whole, such as the bits of a character or the characters of a word, using the same facilities for successive parts.

Shielded twisted pair: A transmission line composed of a twisted 2-wire metallic transmission line surrounded by a sheath of conductive material that protects it from the effects of external fields and confines fields produced within the line. Read more Twisted Pair Cable.

Synchronization bit: A bit used to achieve or maintain synchronism. Note: The term 'synchronization bit' is usually applied to digital data streams, whereas the term 'synchronization pulse' is usually applied to analog signals.

Throughput: The number of bits, characters, or blocks passing through a data communication system, or portion of that system. Note 1: Throughput may vary greatly from its theoretical maximum. Note 2: Throughput is expressed in data units per period of time; e.g., in the DDN, as blocks per second. The maximum capacity of a communications channel or system. 3. A measure of the amount of work performed by a system over a period of time, e.g., the number of jobs per day.

Time-Division Multiplexing (TDM): Digital multiplexing in which two or more apparently simultaneous channels are derived from a given frequency spectrum, i.e., bit stream, by interleaving pulses representing bits from different channels. Note: Successive pulses represent bits from successive channels, e.g., voice channels in a T1 system.

Token: A Token is the permission passed to a node on a bus allowing the node to begin communication on the bus [if required]. A Token is nothing more than a grant to talk on the bus.

Transmission block: A group of bits or characters transmitted as a unit and usually containing an encoding procedure for error control purposes. In data transmission, a group of records sent, processed, or recorded as a unit. Note: A transmission block is usually terminated by an end-of-block character (EOB), end-of-transmission-block character (ETB), or end-of-text character (EOT or ETX).

PC motherboard

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