Subj : Mpost
To : Tobias Ernst
From : Gord Hannah
Date : Mon Jan 06 2003 11:40 am
Following up a message from Gord Hannah to All About [1 of 12] Comm Echo
Primer:
As you requested.
From the commandline:
[H:\mpost]mpostp -Th:\echomaint\commp.txt -Ch:\mpost\mpost.cfg
MPost/2 v2.0a-stable - the Fidonet/Squish/Jam Message Base Writer
(C) Copyright 1992 by CodeLand, All Rights Reserved
Reading H:\Echomaint\Commp.Txt
Writing $H:\Echo\Comm 12/12
Done! (exit 0)
Message base is squish. Squish flatly refuses to toss to the world.
GH> @MSGID: 1:17/23.1 004d2063
GH> @SPLIT: 06 Jan 03 11:38:25 @17/23 18631 01/12 +++++++++++
GH> * Copied (from: COMM) by Gord Hannah using timEd/2 1.10.y2k+.
GH> Fidonet COMM Echo Primer
GH> Revision 1.3.6 12/1/2000
GH> | = Revised Entry + = New Entry
GH> (1) (2)
GH> For newcomers to this, the FidoNet International echo COMM, there
GH> follows a discussion of terms which will be encountered frequently
GH> in the messages herein. A firm grounding in these will add
GH> considerable to understanding the messages in this echo.
GH> +========+ +========+
GH> |Computer| DTE- DCE- DTE- |Computer|
GH> | A | Rate +--A--+ Rate +--B--+ Rate | B |
GH> | |~~~~~~~~~~|Modem|~~~~~~~~~~~~~|Modem|~~~~~~~~~~| |
GH> +========+ +=====+ +=====+ +========+
GH> Pictured above is a brief sketch of a complete signal circuit,
GH> consisting of two computers (A & B) interconnected thru their
GH> Modems.
GH> DEFINITIONS:
GH> 56Kbps Modems [Pre-V.90] - Rockwell, USR, Lucent Technologies, and
GH> Motorola marketed incompatible chipsets/modems that operated in a
GH> server/client format at up to 56Kbps over standard telephone lines
GH> prior to the adoption of ITU-T V.90. USR implemented a protocol
GH> dubbed X2, and the remainder combined efforts to implement a
GH> protocol dubbed K56Flex (a combination of Rockwell's K56Plus and
GH> Lucent's VFlex/2 protocols). The X2 and K56Flex protocols do not
GH> interoperate.
GH> ADSL (Asymmetric Digital Subscriber Line) - a modem technology that
GH> converts existing twisted-pair telephone lines into access paths for
GH> multimedia and high speed data communications. ADSL transmits more
GH> than 6Mbps to a subscriber, and as much as 640 kbps more in both
GH> directions.
GH> An ADSL circuit connects an ADSL modem on each end of a twisted-pair
GH> phone line, creating three information channels; a high speed
GH> downstream channel, a medium speed duplex channel, and a POTS (Plain
GH> Old Telephone Service) channel. The POTS channel is split off from
GH> the digital modem by filters, thus guaranteeing uninterrupted POTS,
GH> even if ADSL fails. The high speed channel ranges from 1.5 to 6.1
GH> Mbps, while duplex rates range from 16 to 640 kbps. Each channel can
GH> be sub-multiplexed to form multiple, lower rate channels.
GH> ARQ - (A)utomatic (R)epeat Re(Q)uest - a general term which
GH> describes detection and retransmission of defective blocks of data.
GH> When appended to a CONNECT string (eg. CONNECT 28800/ARQ) it
GH> indicates that the modems have negotiated some manner of error
GH> control for the link.
GH> ASCII - (A)merican (S)tandard (C)ode for (I)nformation
GH> (I)nterchange. A standard for defining codes for information
GH> exchange between equipment produced by different manufacturers.
GH> ASYNCHRONOUS - Describes data transmission technique in which the
GH> length of time between transmitted characters may vary. Because the
GH> time lapses between transmitted characters may vary, a receiving
GH> modem must be signaled as to when the data bits of a character begin
GH> and when they end. The addition of Start and Stop bits serves this
GH> purpose.
GH> ATM - An international ISDN high-speed, high-volume,
GH> packet-switching transmission protocol standard. ATM uses short,
GH> uniform, 53-byte cells to divide data into efficient, manageable
GH> packets for ultrafast switching through a high-performance
GH> communications network. The 53-byte cells contain 5-byte destination
GH> address headers and 48 data bytes. ATM is the first packet-switched
GH> technology designed from the ground up to support integrated voice,
GH> video, and data communication applications. It is well-suited to
GH> high-speed WAN transmission bursts. ATM currently accommodates
GH> transmission speeds from 64 Kbps to 622 Mbps. ATM may support
GH> gigabit speeds in the future.
GH> BANDWIDTH - The frequency range available for use by modems on an
GH> ordinary two-wire dial-up telephone line. This corresponds to the
GH> frequency range required to reproduce the human voice, or
GH> approximately 3500Hz (200-3700hZ).
GH> BAUD - Perhaps the most mis-used term in all of the discussions
GH> posted in this forum. It actually refers to the unit of measure for
GH> the number of discrete changes of state which occur in a
GH> communication channel per second (ie. the number of times per second
GH> that carrier frequencies are modulated). It is an old term from the
GH> days of Frequency Shift Keyed modems. The name honors Jean Maurice
GH> Emile Baudot, who invented a bit encoding scheme for characters (it
GH> is/was not the same as that presently used for encoding ASCII
GH> characters however).
GH> Relative to FSK modems, the use of Baud referred to the rate that
GH> you could shift from one FSK Tone to another. The tones directly
GH> represented the ones and zeros of data being transmitted. In the
GH> early days they were generally referred to as the Mark Frequency and
GH> the Space Frequency. Accordingly, with this direct correlation of
GH> tones to 1s and 0s, the Baud Rate was the same as the Bit Rate.
GH> [Note: The FSK transmission schemes referenced above are to
GH> bi-frequency implementations such as V.21 and the Bell 103 protocol.
GH> Multi-frequency FSK schemes also exist, but they have not been
GH> widely implemented over the PSTN].
GH> As more complex ways of transmission were devised it was natural to
GH> try to extrapolate this concise definition to define their
GH> operation. An early extrapolation was to Phase Shift Keyed (PSK)
GH> modems such as the V.26 Series of modems. This was unfortunate, but
GH> it did actually occur. The extrapolation went like this: The PSK
GH> modem generated a signal with 4 possible phase states and thus 4
GH> possible phase changes. The states were 0, 90, 180 and 270 degrees
GH> of the carrier. The possible changes were the same.
GH> ___ MPost/2 v2.0a
GH> - Origin: Marsh BBS (c), Dawson Creek, BC Canada (1:17/23.1)
Hope this helps. Keep us posted.
We are a fine board trying to make it better.
http://www.pris.bc.ca/ghannah
[email protected]
Cheers! Gord
-=Team OS/2=-
--- timEd/2 1.10.y2k+
* Origin: Marsh BBS (c), Dawson Creek, BC Canada (1:17/23.1)
