Usrobotics V.34 Manual do Utilizador descarregar pdf (Página 217)

COURIER HIGH SPEED MODEMS

J-8 Glossary

HDLC

High Level Data Link Control. A standard protocol developed

by the International Standards Organization for software appli-

cations and communicating devices operating in synchronous

environments. The protocol defines operations at the link level

of communications, for example, the format of data frames

exchanged between modems over a phone line. See Bisync,

Protocol, SDLC.

HST

High Speed Technology, U.S. Robotics' proprietary signaling

scheme, design and error control protocol for high-speed

modems. HST incorporates trellis-coded modulation, for

greater immunity from variable phone line conditions, and

asymmetrical modulation for more efficient use of the phone

channel at speeds of 4800 bps and above. HST also incorporates

MNP-compatible error control procedures adapted to

asymmetrical modulation.

Hertz, a frequency measurement unit used internationally to

indicate one cycle per second.

ITU-T

International Telecommunication Union-Telecommunication

sector. Formerly referred to as CCITT. An international

organization that defines standards for telegraphic and

telephone equipment. For example, the Bell 212A standard for

1200 bps communication in North America is observed

internationally as ITU-T V.22. For 2400 bps communication,

most U.S. manufacturers observe V.22 bis.

LAPM

Link Access Procedure for Modems, an error control protocol

incorporated in ITU-T Recommendation V.42. Like the MNP

and HST protocols, LAPM uses cyclic redundancy checking

(CRC) and retransmission of corrupted data (ARQ) to ensure

data reliability.

1 2 ... 212 213 214 215 216 217 218 219 220 221 222 ... 244 245

Sem comentários

Usrobotics V.34 Manual do Utilizador Página 217