| slovo | definícia |
modem
(encz) | modem,modem n: Zdeněk Brož |
modem
(encz) | modem,MOdulátor DEModulátor Zdeněk Brož |
modem
(czen) | modem,modemn: Zdeněk Brož |
modem
(gcide) | modulator-demodulator \mod"u*la`tor-de`mod"u*la`tor\, n.
An electronic device that converts electronic signals into
sound waves, and sound waves into electronic signals, used to
transmit information between computers by the use of ordinary
telephone lines; usually called a modem.
[PJC] |
modem
(gcide) | modem \mo"dem\ (m[=o]"d[e^]m), n. [by shortening from
modulator-demodulator.]
An electronic device that converts electronic signals into
sound waves, and sound waves into electronic signals, used to
transmit information between computers by the use of ordinary
telephone lines; also called modulator-demodulator; as, the
latest modems can transmit data at 56,000 baud over a clear
telephone line. The speed of transmission of information by a
modem is usually measured in units of baud, equivalent to
bits per second.
[PJC] |
modem
(wn) | modem
n 1: (from a combination of MOdulate and DEModulate) electronic
equipment consisting of a device used to connect computers
by a telephone line |
modem
(foldoc) | modem
(Modulator/demodulator) An
electronic device for converting between serial data
(typically EIA-232) from a computer and an audio signal
suitable for transmission over a telephone line connected to
another modem. In one scheme the audio signal is composed of
silence (no data) or one of two frequencies representing zero
and one.
Modems are distinguished primarily by the maximum data rate
they support. Data rates can range from 75 bits per second up
to 56000 and beyond. Data from the user (i.e. flowing from
the local terminal or computer via the modem to the telephone
line) is sometimes at a lower rate than the other direction,
on the assumption that the user cannot type more than a few
characters per second.
Various data compression and error correction algorithms
are required to support the highest speeds. Other optional
features are auto-dial (auto-call) and auto-answer which
allow the computer to initiate and accept calls without human
intervention. Most modern modems support a number of
different protocols, and two modems, when first connected,
will automatically negotiate to find a common protocol (this
process may be audible through the modem or computer's
loudspeakers). Some modem protocols allow the two modems to
renegotiate ("retrain") if the initial choice of data rate is
too high and gives too many transmission errors.
A modem may either be internal (connected to the computer's
bus) or external ("stand-alone", connected to one of the
computer's serial ports). The actual speed of transmission
in characters per second depends not just the modem-to-modem
data rate, but also on the speed with which the processor can
transfer data to and from the modem, the kind of compression
used and whether the data is compressed by the processor or
the modem, the amount of noise on the telephone line (which
causes retransmissions), the serial character format
(typically 8N1: one start bit, eight data bits, no
parity, one stop bit).
See also acoustic coupler, adaptive answering, {baud
barf}, Bulletin Board System, Caller ID, SoftModem,
U.S. Robotics, UUCP, whalesong.
Usenet newsgroup: news:comp.dcom.modems.
(2002-05-04)
|
modem
(vera) | MODEM
MOdulator DEModulator
|
| | podobné slovo | definícia |
modems
(encz) | modems,modemy n: pl. Zdeněk Brož |
modemy
(czen) | modemy,modemsn: pl. Zdeněk Brož |
Homodemic
(gcide) | Homodemic \Ho`mo*dem"ic\, a. [Homo- + 1st deme, 2.] (Biol.)
A morphological term signifying development, in the case of
multicellular organisms, from the same unit deme or unit of
the inferior orders of individuality.
[1913 Webster] |
Incommodement
(gcide) | Incommodement \In`com*mode"ment\, n.
The act of incommoded. [Obs.] --Cheyne.
[1913 Webster] |
acoustic modem
(wn) | acoustic modem
n 1: a modem that converts electrical signals to telephone tones
and back again |
cable modem
(foldoc) | cable modem
A type of modem that allows
people to access the Internet via their cable television
service.
A cable modem can transfer data at 500 kbps or higher,
compared with 28.8 kbps for common telephone line modems, but
the actual transfer rates may be lower depending on the number
of other simultaneous users on the same cable.
Industry pundits often point out that the cable system still
does not have the bandwidth or service level in many areas
to make this feasible. For example, it has to be capable of
two-way communication.
See also: DOCSIS.
(2000-12-19)
|
link access protocol for modems
(foldoc) | Link Access Protocol for Modems
LAPM
(LAPM) The Automatic Repeat Request system used in the
V.42 protocol.
|
modem7
(foldoc) | MODEM7
A batch file transfer protocol.
See also XMODEM.
(1995-05-02)
|
null modem
(foldoc) | null modem
A cable, especially an EIA-232
cable, for connecting serial ports on two computers directly,
rather than via modems. Since, according to the
specification, both computers should transmit on pin three of
their EIA-232 connectors and receive on pin two, a null modem
cable needs to connect one computer's pin two to the other's
pin three and vice versa. It also needs to have male
connectors at both ends (again, according to the
specification).
(1996-05-17)
|
softmodem
(foldoc) | SoftModem
The integration of modem controller and data pump
algorithms into a single RAM-based DSP hardware
architecture. These integrated algorithms are stored on the
computer's hard disk, from which they are downloaded into the
DSP board's random-access memory (RAM). This downloading, or
"booting" process of the PC-installed software algorithms
occurs as part of the computer's power-up initialisation
process in less than 100 milliseconds, making it transparent
to the user.
[Digicom Modem FAQ version 2.03].
|
xmodem
(foldoc) | XMODEM
Ward Christensen's file transfer
protocol, probably the most widely available protocol used
for file transfer over serial lines (e.g. between modems).
XMODEM uses 128-byte packets with error detection,
allowing the receiver to request retransmission of a corrupted
packet. XModem is fairly slow but reliable.
Several variations have been proposed with increasing packet
sizes (e.g. XMODEM-1K) and different error detection (CRC
instead of checksum) to take advantage of faster modems.
Sending and receiving programs can negotiate to establish the
best protocol they both support.
John Mahr wrote the original XMODEM CRC error correction code.
This implementation was backward compatible with Christensen's
original checksum code. It improved the error detection from
98% to 99.97% and improved the reliability of transmitting
binary files.
Standard XMODEM specifies a one-second timeout during the
reception of characters in the data block portion of a packet.
Chuck Forsberg improved upon XMODEM by developing YMODEM and
ZMODEM.
[Chuck Forsberg, "XMODEM/YMODEM Protocol Reference"].
(2005-09-16)
|
xmodem-1k
(foldoc) | XMODEM-1K
A version of XMODEM using 1 kilobyte packets.
|
ymodem
(foldoc) | YMODEM
A file transfer protocol used between modems. YMODEM was
developed by Chuck Forsberg as the successor to XMODEM and
was itself succeeded by ZMODEM. XMODEM used 128-byte
packets, YMODEM can also use 1 kilobyte packets. Whereas
YMODEM is a batch protocol, YMODEM-G is a non-stop version.
File sizes are included in the YMODEM header when sending both
binary and text files. Thus files transferred via YMODEM
should preserve their exact length. File modification times
may also be present in the YMODEM header.
YModem can fall back to smaller packets when necessary but
there is no backward compatibility with XModem's error
detection.
[Chuck Forsberg, "XMODEM/YMODEM Protocol Reference"].
(1995-02-02)
|
ymodem-g
(foldoc) | YMODEM-G
A non-stop "streaming" version of YMODEM designed for
"error-free" connections with proper flow control; the
transmitting program sends packets to the receiver as fast as
it can without waiting for acknowledgements. Any errors cause
the entire file transfer to abort.
|
zmodem
(foldoc) | ZMODEM
A file transfer protocol with error checking and
crash recovery. Developed by Chuck Forsberg. Its transfer
rate is similar to YMODEM-g. Like YMODEM-g, ZMODEM does not
wait for positive acknowledgement after each block is sent,
but rather sends blocks in rapid succession. If a ZMODEM
transfer is cancelled or interrupted for any reason, the
transfer can be resurrected later and the previously
transferred information need not be resent.
{FTP Oakland
(ftp://oak.oakland.edu/pub/simtelnet/msdos/zmodem/)}, {FTP PDX
(ftp://ftp.cs.pdx.edu/pub/zmodem/)}.
Telephone: +1 900 737 7836.
(1996-07-02)
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