User guide

76
MTPSR3-100 User Guide
Stop Bit: One of the variables used for timing in asynchronous
data transmission. Depending on the devices, each character
may be trailed by 1, 1.5, or 2 stop bits.
Superframe (D4): A T1 transmission format that consists of 12
DS1 frames, or 2316 bits. A DS1 frame consists of 193 bit
positions. A frame overhead bit is in the first position, and it is
used for frame and signaling phase alignment only.
Subscriber Loop: See “Local loop”.
Switched 56: A circuit-switched (full duplex digital synchronous
data transmission) service that lets you dial a number and
transmit data to it at 56K bps. It is a relatively low cost service,
widely used in North America for telecommuting,
videoconferencing and high speed data transfers. Many phone
companies are (or will be) phasing out Switched 56 in favor of
ISDN service.
Switched Virtual Circuit (SVC): A type of data transmission
where the connection is maintained only until the call is cleared.
Switched Line: In communications, a physical channel
established by dynamically connecting one or more discrete
segments. This connection lasts for the duration of the call after
which each segment can be used as part of a different channel.
Contrast with leased line.
Switched Network: A network in which a temporary connection
is established from one point via one or more segments.
Synchronous Data Link Control (SDLC): A discipline
conforming to subsets of the Advanced Data Communications
Control Procedures (ADCCP) of the American National
Standards Institute (ANSI) and High-level Data Link Control
(HDLC) of the International Organization for Standardization, for
managing synchronous, code-transparent, serial-by-bit
information transfer over a link connection. Transmission
exchanges may be duplex, or half-duplex over switched or
nonswitched links. The configuration of the link connection may
be point-to-point, multipoint, or loop.
Synchronous Transmission: The transmission of data which
involves sending a group of characters in a packet. This is a
common method of transmission between computers on a
network or between modems. One or more synchronous
characters are transmitted to confirm clocking before each
packet of data is transmitted. Compare to Asynchronous
Transmission.
Systems Network Architecture (SNA): The description of the
logical structure, formats, protocols, and operational sequences
for transmitting information units through, and controlling the
configuration and operation of networks.
T
Tariff: The rate/availability schedule for telephone and ISDN
services from a regulated service provider.
TCP/IP: A set of communication protocols that support peer-to-
peer connectivity functions for both local and wide area
networks.
T Carrier: The generic name for a digitally multiplexed carrier
system. In the North American digital hierarchy, a T is used to
designate a DS (digital signal) level hierarchy. Examples: T1
(DS1) is a 1.544 M bps 24-channel designation. In Europe, T1 is
called E1. The T Carrier system was originally designed for
transmitting digitized voice signals, but has since been adapted
for digital data applications.
T1: A digital transmission link capable of 1.544M bps. T1 uses
two pairs of normal UTP, and can handle 24 voice conversations,
each digitized at 64K bps. T1 is a standard for digital
transmission in the U.S., Canada, Japan and Hong Kong. T1 is
the access method for high-speed services such as ATM, frame
relay, and SMDS. See also T Carrier, T1 line and FT1.
T1 Channel Tests: A set of diagnostics that vary by carrier, used
to verify a T1 channel operation. Can include Tone, Noise Level,
Impulse Noise Level, Echo Cancelers, Gain, and Crosstalk
testing.
T1 Framing: To digitize and encode analog voice signals
requires 8000 samples per second (twice the highest voice
frequency of 4000 Hz). Encoding in an 8-bit word provides the
basic T1 block of 64K bps for voice transmission. This “Level 0
Signal, as its called, is represented by “DS-0”, or Digital Signal at
Level 0. 24 of these voice channels are combined into a serial bit
stream (using TDM), on a frame-by-frame basis. A frame is a
sample of all 24 channels; so adding in a framing bit gives a
block of 193 bits (24x8+1=193). Frames are transmitted at 8000
per second (the required sample rate), creating a 1.544M
(8000x193=1.544M) transmission rate.
T1 Line: A digital communications facility that functions as a 24-
channel pathway for data or voice transmission. A T1 line is
composed of two separate elements: the Access element and
the Long Haul element.
T1 Mux: A device used to carry many sources of data on a T1
line. The T1 mux assigns each data source to distinct DS0 time
slots within the T1 signal. Wide bandwidth signals take more
than one time slot. Normal voice traffic or 56/64K bps data
channels take one time slot. The T1 mux may use an internal or
external T1 DSU; a “channel bank” device typically uses an
external T1 CSU.
Transmission Control Protocol / Internet Program (TCP/IP): A
multi-layer set of protocols developed by the US Department of
Defense to link dissimilar computers across dissimilar and
unreliable LANs.
Terminal: The screen and keyboard device used in a mainframe
environment for interactive data entry. Terminals have no “box”,
which is to say they have no file storage or processing
capabilities.
Terminal Adapter (TA): An ISDN DTE device for connecting a
non-ISDN terminal device to the ISDN network. Similar to a
protocol converter or an interface converter, a TA connects a
non-ISDN device between the R and S interfaces. Typically a PC
card.
Tie line: A dedicated circuit linking two points without having to
dial a phone number (i.e., the line may be accessed by lifting the
telephone handset or by pushing a button).
Time-Division Multiplexing (TDM): Division of a transmission
facility into two or more channels by allotting the common
channel to several different information channels, one at a time.
Time Slot: One of 24 channels within a T1 line. Each channel
has a 64K bps maximum bandwidth. “Time slot” implies the time
division multiplexing organization of the T1 signal.
Toll Call: A call to a location outside of your local service area
(i.e., a long distance call).
Tone dialing: One of two methods of dialing a telephone,
usually associated with Touch-Tone® (push button) phones.
Compare with pulse dialing.