电信专业英英词典S-3（在线收听）

　　SSN

　　switched service network

　　SS

　　signaling system

　　Station Equipment

　　Station equipment is a component of telecommunications systems such as a telephone or data terminal, generally located on the user's premises. Its function is to transmit and receive user information (traffic), and to exchange control information with the network to access communications services.

　　STM

　　synchronous transfer mode

　　STP

　　shielded twisted pair or signaling transfer/point

　　Superframe Format (SF)

　　Superframe format is a framing format (D3/D4——mode 3), the most widely used T1 carrier framing format in which the bipolar bit stream is organized into superframes each consisting of 12 frames. To ensure timing, the signal must consist of at least one "1" bit in every 15 bits and at least :3 " 1" bits in every 24 bits. See extended superframe.

　　Supervisory Signals

　　Supervisory signals are signals used to indicate or control the states of circuits involved in a particular switched connection. A supervisory signal indicates to equipment, to an operator, or to a user that a particular state in the call has been reached and may simplify the need for action.

　　Switch Matrices

　　Switch matrices are the mechanism that provides signal paths between its input and output terminations. Modern matrices are electronic and involve either time or space division switching. A time division switch employs a TDM process, in a time-slot interchange (TSI) arrangement. In space division, a physical, electrical, spatial link is established through the switch matrix. Whereas older space division switches used electro-mechanical mechanisms with metallic contacts, modern space-division switches are implemented electronically using integrated circuits.

　　Switching

　　Switching refers to the process of connecting appropriate lines and/or trunks to form a desired communications path between two station sets, or more generally, any two arbitrary points in a telecommunications network. Included are all kinds of related functions such as signaling, monitoring the status of circuits, translating address to routing instructions, alternate routing, testing circuits for busy conditions, and detecting and recording troubles.

　　Switching Systems

　　Switching systems are interconnect transmission facilities at various network locations and route traffic through a network.

　　Systems (Manual Circuits)

　　In Plant Records and Assignment, these terms refer to circuits whose network elements have been assigned manually rather than by automatic assignment.

　　Systems Network Architecture (SNA)

　　SNA is IBM's proprietary description of the logical structure, formats, protocols, and operational sequences for transmitting information units through and controlling network configuration and operation.

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