SoundExpression SE14SRS, Руководство пользователя

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command mode . The modem is in command
mode when it is turned on or reset, when it
loses its connection to a remote modem,
when it is in on-line mode, or when escape
characters (+++) are typed. To transmit data,
the modem must be in data mode. The
modem does not transmit data when in
command mode.
communications protocol . A set of
procedures which controls how a data
communications network operates.
D
DCD . Data Carrier Detect. Indicates to the
terminal device that the modem is receiving a
valid carrier signal from a remote modem.
The carrier is a tone at a specified frequency.
DCE . Data Communications Equipment. The
local and/or remote modem. A DCE is
usually connected to a DTE.
DTE . Data Terminal Equipment. The
computer or terminal, either local (yours), or
the remote (the one you’re communicating
with). A DTE is usually connected to a DCE.
DTR . Data Terminal Ready. The computer
issues this signal to the attached modem
indicating that it is ready to receive data.
data compression
. A technique that examines
transmitted data for redundancy and replaces
strings (groups) of characters with special
codes which the receiving modem interprets
and restores to its original form. Transmission
of compressed data results in shorter connect
times and hence cost savings for connect
charges. Data compression is sometimes
called “source encoding”.
data mode . The modem is in data mode when
a connection has been established with a
remote modem and sends a CONNECT
response confirming the connection. User
data may then be transmitted or received.
dial modifier . Dial modifiers are special
characters appended to the ATD command
which instruct the modem how to place a
call.
digital signa l. A discrete signal which can
only take on one of several (usually only two)
discrete levels in contrast to analog signals
which can take a continuous range of levels.
E
error detection and correction
. The
transmitting modem attaches a special pattern
(called a frame check sequence) calculated
according to a prescribed algorithm from
user-defined data to the end of a block of
data. The receiving modem performs the
same algorithm and compares it to the one
with the transmitted data. If these match,
then the block of data has been received
correctly. If not, the block of data is re-
transmitted until no errors are detected.
escape sequence . Also referred to as the
escape command. This special command is
entered as three plus symbols (+++) and
places the modem in command mode and
interrupts user data transmission, but does
not terminate the data connection. This allows
the entering of commands while the
connection is maintained.
extended AT-command . Extended commands
were developed to provide greater
functionality and control over modem
operations than is available from the basic AT
command set.
Glossaries