（单词翻译:单击）
SSN
switched service network
SS
signaling system
Station Equipment
Station equipment is a component1 of telecommunications systems such as a telephone or data terminal, generally located on the user's premises2. Its function is to transmit and receive user information (traffic), and to exchange control information with the network to access communications services.
STM
synchronous4 transfer mode
STP
shielded twisted pair or signaling transfer/point
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 timing5, 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 mechanism6 that provides signal paths between its input7 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, spatial8 link is established through the switch matrix. Whereas older space division switches used electro-mechanical mechanisms9 with metallic10 contacts, modern space-division switches are implemented11 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 recording12 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 proprietary13 description of the logical structure, formats14, protocols15, and operational sequences for transmitting information units through and controlling network configuration16 and operation.
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