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MultiModem ZPX User Guide 43

T1 Channel Tests: A set of diagnostics that vary by carrier, used to

verify a T1 channeloperation. 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 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 transmission. A T1 line is

composed of twoseparate elements: the Accesselement and the

Long Haul element.

T1 Mux: A device used to carry many sources of data on a T1 line.

The T1 mux assignseach datasource to distinct DS0 time slots

within theT1 signal. Widebandwidthsignals takemore 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

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 64 Kbps 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.

Topology: Physical layout of network components (cables,

stations, gateways, and hubs). Three basic interconnection

topologies are star, ring, and bus networks.

Transmission Control Protocol (TCP): A communications

protocol used in Internet and in any network that follows the US

Department of Defense standards for internetwork protocol. TCP

provides a reliable host-to-host protocol between hosts in

packet-switched communications networks and in

interconnected systems of such networks. It assumes that the

Internetprotocol is the underlyingprotocol.

Transport Layer: Layer 4 of the Open Systems Interconnection

(OSI) model; provides reliable, end-to-end delivery of data, and

detects transmission sequential errors.

Transport Protocol Data Unit (TPDU): A transport header, which

is added to every message, contains destination and source

addressing information that allows the end-to-end routing of

messages in multi-layer NAC networks of high complexity. They

are automatically added to messages as they enter the network

and can be stripped off before being passed to the host or

another device that does not support TPDU’s.

Trunk: Transmission links that interconnect switching offices.

TSR (terminate and stay resident): A software program that

remains active and in memory after its user interface is closed.

Similar to a daemon in UNIX environments.

Tunneling: Encapsulation data in an IP packet for transport across

the Internet.

Twisted pair wiring: A type of cabling with one or more pairs of

insulated wires wrapped around each other. An inexpensive

wiring method used for LAN and telephone applications, also

called UTP wiring.

Type A: The upstream (USB Type A) connector. A Type A

Connector is for those devices on which the external cable is

permanently attached. Connectors for USB come in two designs:

the 'A' and 'B' types. Upstream connections (computer, hub

input, etc.) are made using the 'A' type connector, downstream

connections (peripherals, hub outputs) are made using the 'B'

type connector. The USB spec defines two types of connectors to

protect the bus from illegal topologies (e.g., connecting one

downstream port back to another, etc.) and to prevent end-user

confusion. This allows end users to easily attach the correct

connectors to peripherals and ports. Type A Plug and receptacle

are to be used for those devices on which the external cable is

permanently attached to devices such as Keyboard, mouse and

hubs. Series B Plug and receptacle are to be used for those

devices that require an external detachable cable such as

printers, scanners and modems.

Type B: The uplink (USB Type B) connector. A Type B Connector

is for detachable external cables. Allows for double ended cable

assemblies. Connectors for USB come in two designs: the 'A' and

'B' types. Upstream connections (computer, hub input, etc.) are

made using the 'A' type connector, downstream connections

(peripherals, hub outputs) are made using the 'B' type connector.

The USB spec defines two types of connectors to protect the bus

from illegal topologies (e.g., connecting one downstream port

back to another, etc.) and to prevent end-user confusion. This

allows end users to easily attach the correct connectors to

peripherals and ports. Type A Plug and receptacle are to be used

for those devices on which the external cable is permanently

attached to devices such as Keyboard, mouse and hubs. Series B

Plug and receptacle are to be used for those devices that require

an external detachable cable such as printers, scanners and

modems.

UART (Universal Asynchronous Receiver/Transmitter)

(pronounced “you art”): A chip that transmits and receives data

on the serial port. It converts bytes into serial bits for

transmission, and vice versa, and generates and strips the start

and stop bits appended to each character.

UHCI (Universal Host Controller Interface): The USB Universal

Glossary

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