Black-box 5000 User Manual download pdf (Page 254)

Multiserver 5000

252

ABR, autobaud rate detection — A process by which

a receiving device determines the data rate,

code level, and stop bits of incoming data by

examining the first character received (usually a

preselected sign-on character). ABR allows a

receiving device to accept data from a variety of

transmitting devices operating at different data

rates, which means that the receiver does not

need to be configured for each specific data

rate in advance.

ACK, acknowledgment — A control character used

as a reply in communications protocols. For

example, in the Hewlett-Packard ENQ/ACK

protocol, ACK is sent by the receiving device as a

reply to ENQ sent by the transmitting device.

ADB, automatic dial backup — A modem feature

that enables it to automatically switch data

transmission from the leased lines to dial lines

when line impairments on the leased lines reach

an unacceptable level. The modem also returns

to leased-line operation when the conditions of

those lines improve.

aggregate input rate — The sum of all data rates of

terminals and computer ports connected to a

multiplexer. “Burst aggregate input rate” is the

instantaneous maximum data input rate

accepted by the multiplexer.

analog — Continuously variable as opposed to

discretely variable. Physical quantities, such as

temperatures, are continuously variable and are

described as analog; analog signals vary in

accordance with the physical quantities they

represent. The public telephone network was

designed to transmit voice in analog form.

analog loopback — A diagnostic test that forms the

loop at the modem’s telephone line interface.

answer tone — A signal sent by the called modem

(the answer modem) to the calling modem (the

originate modem) on public telephone

networks that indicates the called modem’s

readiness to accept data.

answer tone frequency — The frequency (cycles per

second) of the answer tone.

APV, Advanced Packetized Voice — Low Bit Rate

Voice (LBRV) digitizing technique that

produces acceptable-quality voice signals and

requires a bandwidth of only 9.6 Kbps.

ARQ, automatic request for retransmission — An

error-control method in which the receiving

device informs the transmitting device which

transmission blocks were received successfully.

The transmitting device retransmits any blocks

not successfully received.

ASCII, American Standard Code for Information

Interchange — A 7-bit-plus-parity character set

or code established by the American National

Standards Institute (ANSI) to achieve

compatibility between data services.

async — Short for asynchronous. See asynchronous

transmission.

asynchronous transmission — A method of sending

data in which the interval between characters

may be of unequal length. The characters

transmitted include a start bit and one or more

stop bits, which define the beginning and

ending of the character. No synchronizing or

timing signals need to be sent.

attenuation — Deterioration of signal strength as it

passes through a transmission medium;

generally attenuation increases with both

frequency and cable length. Attenuation is

measured in terms of decibels.

bar graph — A visual indication of the input signal

level strength in dB, as displayed on the

command port or by the four red indicators on

the voice/fax channel.

baud — A unit of signalling speed. The speed in

baud is the number of discrete conditions or

signal events per second. If each signal event

represents one bit, the baud rate is the same as

bps. If each signal event represents more than

Glossary

1 2 ... 249 250 251 252 253 254 255 256 257 258 259 ... 267 268

Comments to this Manuals

No comments

Black-box 5000 User Manual Page 254

Comments to this Manuals