Motorola 326X V.34 - Manual (Page 230)

4-Glossary
Glossar
y
ITU V.24 An electrical standard for interconnecting data communications equipment and data
terminal equipment established by the ITU. It is the most commonly used computer/modem
interface. Nearly equivalent to EIA/TIA 232-D.
ITU V.25 bis An ITU-specified serial Auto-Call Unit (ACU) for operation with both asynchronous and
synchronous DTE equipment.
ITU V.32 The standard for 2-wire, full-duplex modems operating at up to 9600 bps for use on the
general switched telephone network and on leased telephone circuits.
ITU V.32 bis A modulation standard that extends the speed of 2-wire leased line and 2-wire dial line
modems to include 14.4 and 12.0 kbps. It is backwards-compatible with the V.32
modulation mode. When operating in the V.32 bis modulation mode, the modem supports
synchronous and asynchronous transmission rates of 4.8, 7.2, 9.6, 12.0, and 14.4 kbps.
ITU V.42 Used with full-duplex asynchronous data transmission, V.42 is an ITU-adopted standard
which specifies two methods of error correction for modems: MNP 4 and LAPM (Link
Access Protocol for Modems).
ITU V.42 bis Used with full-duplex asynchronous data transmission, V.42 bis is a high-performance data
compression algorithm based on the Lempel-Ziv Data Compression algorithm. This
compression technique is not compatible with MNP 5 or other MNP levels. The theoretical
limit of V.42 bis is 4:1 compression. The actual compression (throughout) that is achieved
with any algorithm, including V.42 bis is data (file) dependent. Using V.42 bis, the modem
continuously monitors the compressibility of user data. If user data is not compressible, the
V.42 bis algorithm detects this condition and automatically turns data compression off, so
the data link rate is never less than the modem modulation rate.
ITU-TS V.34 V.34 is a four-dimensional trellis-coded modulation standard using precoding and
pre-emphasis equalization schemes.
Interface A shared connection or boundary between two devices or systems. The point (logical or
physical) at which two devices or systems are linked.
LAPM Link Access Protocol for Modems. An ITU link layer protocol for modems.
Leased line A dedicated telephone-line circuit permanently connecting two or more locations and used
solely by one customer, who leases the line.
LED Light Emitting Diode.
Loopback (1) A method of feeding a received signal back from a point in a data link to the receiver at
the site where the data was originated. Commonly used to test portions of a data link to
isolate faulty equipment or data lines. (2) The feeding back of data from a point in a data
path to the transmitting source for testing. (3) A diagnostic procedure that sends a test
message back to the originator, which compares the message with the original transmission.
Loopback testing can occur within a locally attached device or can be conducted remotely
over a communications circuit.
LPDA2 Feature that enables the 326X to be used in an IBM dial and leased line restoral applications
using LPDA2 Dial and Disconnect commands.
Modem Modulator/demodulator, enabling digital data to be sent over analog transmission facilities.