Definitions and Terms Digital Telephone Switching System Part 7

Some of the definitions and terms associated with Central Office (CO) digital telephone switching systems are defined below:

Definitions and Terms Digital Telephone Switching System Part 7

Sidetone: The portion of a talker’s signal that is purposely fed back to the earpiece so that the talker hears his or her own speech.
Signaling: The exchange of electrical information (other than by speech) specifically concerned with the establishment and control of connections and management in a communication network.
Significant instants: The instants at which a digital line code changes state. (The boundaries of a signal interval).
Simplex Transmission: A mode of operation involving transmission in one direction only.
Singing: An audible oscillation of a telephone circuit caused by a net amount of gain in a four-wire segment of the circuit.
Singing Return Loss (SRL): A loss due to impedance mismatch particularly at the junctions between interconnected circuits. (For more details see also “Echo Return Loss”).
SLIC: Subscriber Line Interface Circuit.
Slip: At the interface between two digital systems, slip is the insertion or deletion of data into or from the data stream caused by an offset in clock frequencies.
Space Diversity: In radio systems, the use of two receiving antennas and possibly two separate receivers to provide protection against atmosphere included signal attenuation (fading).
Span Line: A repeated T1/E1 line from end to end but not including channel banks.
Speech Digit Dialing (robbed digit signaling): Signaling in which digit time slots, primarily used for the transmission of encoded speech, are periodically used for signaling.
Speech Dialing: The use of a short address code to represent an often-called telephone number. The common control computer in a PABX or end office switching system, providing such a service, translates the short code into the desired number.
Star Network: A network with a single node to which all other nodes are connected.
State Store: A memory map of the connection status of a switching matrix.
STS: Space-Time-Space digital switching structure.
Stuffing Character: A character used on isochronous transmission links to take account of differences in clock frequencies.

Signal: A signal used to indicate the status of a line or to control equipment on the line.
Synchronous: Two signals are synchronous if their corresponding significant instants have a desired phase relationship.
Synchronous Network: A network in which the clocks are controlled so as to run, ideally, at identical rates, or at the same mean rate with limited relative phase displacement.
Synchronous Transmission: A mode of digital transmission in which discrete signal elements (symbols) are transmitted at a fixed and continuous rate.
Talkoff: An inadvertent disconnect caused by speech sounds being interpreted as in-channel control signals (disconnects).
Tandem Office: In general, any intermediate switch used to establish a connection. In specific terminology, a tandem office is a switch used to interconnect end offices in an exchange area.
TASI: Time Assignment Speech Interpolation, is the practice of concentrating a group of voice signals, onto a smaller group of channels, by dynamically switching active voice signals to idle channels.
Ternary Coding: The use of all states of a three-level code to send more than one bit of information in a single symbol. This is in contrast to bipolar coding, which uses three levels, but only one of two in any particular interval. One method of interfacing binary data to a ternary line code is to encode 4 bits with three ternary symbols (4B-3T).
Tie Line: A dedicated circuit connecting two private branch exchanges.
Time Congestion: The ratio of time that all facilities of a system are busy (congested). Time congestion refers to the status of the system and does not necessarily imply that blocking occurs.
Time Division Multiplexing (TDM): TDM is sharing a transmission link among multiple users by assigning time intervals to individual users during which they have the entire bandwidth of system.
Time Expansion: The use of more time slots on internal links of a switch than exist on external links.
Time Out: A network parameter related to an enforced event designed to occur at the conclusion of a predetermined elapsed time.
Tip and Ring Conductors: The two conductors associated with a 2-wire cable pair. Page 21 of 96
The terms tip and ring deliver their names from the physical characteristics of an operator’s cord-board plug, in which these two conductors terminated in the days of manual switchboards.


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