Multitech MTPSR1-202ST Podręcznik Użytkownika Pobierz pdf (Strona 102)

ProxyServer User Guide

102

MTPSR1-202ST

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 configura-

tion and operation of networks.

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 applica-

tions.

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 64 Kbps. 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 Cancellers, 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 64

Kbps 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. 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 56/64 Kbps 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 multilayer set of protocols devel-

oped 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 64 Kbps maximum bandwidth.

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