Robotics Sportster Flash x2 Instrukcja Użytkownika Pobierz pdf (Strona 14)

Appendix C - Glossary

analog-to-digital converter (ADC)

A device that samples incoming analog voltage waveforms, rendering them as

sequences of binary digital numbers. Passing waveforms through an ADC

introduces quantization noise.

basic rate interface (BRI)

An ISDN line that provides up to two 64-Kbps B-channels and one 16-Kbps D-

channel over an ordinary two-wire telephone line. B-channels carry circuit-oriented

data or voice traffic while D-channels carry call-control signals.

call-control signaling

Operations associated with establishing and tearing down virtual circuits through a

network. For example, dialing.

central office (CO)

The facility at which individual telephone lines in a limited geographic area are

connected to the public telephone network.

codec

Coder-decoder -- a device that converts analog signals on one side to digital signals

on the other, or vice versa.

digital loop carrier (DLC)

A device that, when used in concert with a digital line, provides an alternative to

stretching multiple lower-bandwidth analog lines over longer distances.

digital pad

A sort of fixed “volume control” that attempts to equalize the loudness of signals

from various types of lines.

digital-to-analog converter (DAC)

A device that reconstructs analog voltage waveforms from an incoming sequence of

binary digits. Does not in itself introduce noise.

digital signal processor (DSP)

A processor that is optimized for performing the complex mathematical

calculations inherent in processing digital signals. A discrete DSP may be

reprogrammed. A DSP integrated in a chipset typically contains its own ROM and

cannot be reprogrammed.

high-end rolloff

Reduction in signal power at the upper frequencies of the voiceband.

line-side T1

A T1 that undergoes at least one analog-to-digital conversion in the path between

the x2 server modem and the PSTN.

load coil

Used to offset some of the negative effects of longer local loop lengths on voice

transmission. Load coils improve voice quality but reduce data-carrying capacity,

especially at V.34 and x2 speeds.

local loop

The path (wiring) between a customer location and the local telephone company’s

central office. This is often a completely analog connection over two copper wires.

near-end echo

Interference in the receive signal caused by reflection of the transmit signal from

the “hybrid” at the local CO.

primary rate interface (PRI)

A four-wire ISDN line (or "trunk") with the same capacity as a T1, 1.544 Mbps.

PRIs contain 23 64-Kbps B-channels and one 64-Kbps D-channel. The D-channel

carries call-control signaling for all the B-channels.

private branch exchange (PBX)

A telephone switch that is privately owned and located on a customer’s premises --

typically a business or hotel.

signal-to-noise ratio (SNR)

A measure of link performance arrived at by dividing signal power by noise power.

Typically measured in decibels. The higher the ratio, the clearer the connection.

A four-wire digital line (or "trunk") with the same capacity as a PRI line, 1.544

Mbps. T1s contain 24 DS0s, each of which carries 56 Kbps (call-control signaling

is carried within the DS0).

trunk-side T1

A T1 line that has a direct digital connection to the phone network, and therefore

undergoes no analog conversions in the path between the x2 server modem and the

PSTN.

x2 client modem

A modem equipped with x2 software that is attached to a standard analog

telephone line. In order to connect at x2 speeds (32–56 Kbps), the device at the

other end of the connection must be an x2 server modem that is attached to a trunk-

side T1, BRI, or PRI line.

x2 server modem

A digital modem equipped with x2 software that is attached to a trunk-side T1,

BRI, or PRI line. Client modems must be equipped with x2 software in order to

connect at x2 speeds (32–56 Kbps). Current products that can act as x2 servers

include the Total Control Enterprise Network Hub, NETServer I-modem, MP I-

modem and Courier I-modem.

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