• Mpost

    From Gord Hannah@1:17/23.1 to Tobias Ernst on Monday, January 06, 2003 11:40:20
    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.

    @MSGID: 1:17/23.1 004d2063
    @SPLIT: 06 Jan 03 11:38:25 @17/23 18631 01/12 +++++++++++
    * Copied (from: COMM) by Gord Hannah using timEd/2 1.10.y2k+.

    Fidonet COMM Echo Primer
    Revision 1.3.6 12/1/2000

    | = Revised Entry + = New Entry
    (1) (2)

    For newcomers to this, the FidoNet International echo COMM, there
    follows a discussion of terms which will be encountered frequently
    in the messages herein. A firm grounding in these will add
    considerable to understanding the messages in this echo.

    +========+ +========+ |Computer| DTE- DCE- DTE- |Computer|
    | A | Rate +--A--+ Rate +--B--+ Rate | B |
    | |~~~~~~~~~~|Modem|~~~~~~~~~~~~~|Modem|~~~~~~~~~~| | +========+ +=====+ +=====+ +========+

    Pictured above is a brief sketch of a complete signal circuit,
    consisting of two computers (A & B) interconnected thru their


    56Kbps Modems [Pre-V.90] - Rockwell, USR, Lucent Technologies, and
    Motorola marketed incompatible chipsets/modems that operated in a server/client format at up to 56Kbps over standard telephone lines
    prior to the adoption of ITU-T V.90. USR implemented a protocol
    dubbed X2, and the remainder combined efforts to implement a
    protocol dubbed K56Flex (a combination of Rockwell's K56Plus and
    Lucent's VFlex/2 protocols). The X2 and K56Flex protocols do not interoperate.

    ADSL (Asymmetric Digital Subscriber Line) - a modem technology that converts existing twisted-pair telephone lines into access paths for multimedia and high speed data communications. ADSL transmits more
    than 6Mbps to a subscriber, and as much as 640 kbps more in both directions.

    An ADSL circuit connects an ADSL modem on each end of a twisted-pair
    phone line, creating three information channels; a high speed
    downstream channel, a medium speed duplex channel, and a POTS (Plain
    Old Telephone Service) channel. The POTS channel is split off from
    the digital modem by filters, thus guaranteeing uninterrupted POTS,
    even if ADSL fails. The high speed channel ranges from 1.5 to 6.1
    Mbps, while duplex rates range from 16 to 640 kbps. Each channel can
    be sub-multiplexed to form multiple, lower rate channels.

    ARQ - (A)utomatic (R)epeat Re(Q)uest - a general term which
    describes detection and retransmission of defective blocks of data.
    When appended to a CONNECT string (eg. CONNECT 28800/ARQ) it
    indicates that the modems have negotiated some manner of error
    control for the link.

    ASCII - (A)merican (S)tandard (C)ode for (I)nformation
    (I)nterchange. A standard for defining codes for information
    exchange between equipment produced by different manufacturers.

    ASYNCHRONOUS - Describes data transmission technique in which the
    length of time between transmitted characters may vary. Because the
    time lapses between transmitted characters may vary, a receiving
    modem must be signaled as to when the data bits of a character begin
    and when they end. The addition of Start and Stop bits serves this

    ATM - An international ISDN high-speed, high-volume,
    packet-switching transmission protocol standard. ATM uses short,
    uniform, 53-byte cells to divide data into efficient, manageable
    packets for ultrafast switching through a high-performance
    communications network. The 53-byte cells contain 5-byte destination address headers and 48 data bytes. ATM is the first packet-switched technology designed from the ground up to support integrated voice,
    video, and data communication applications. It is well-suited to
    high-speed WAN transmission bursts. ATM currently accommodates
    transmission speeds from 64 Kbps to 622 Mbps. ATM may support
    gigabit speeds in the future.

    BANDWIDTH - The frequency range available for use by modems on an
    ordinary two-wire dial-up telephone line. This corresponds to the
    frequency range required to reproduce the human voice, or
    approximately 3500Hz (200-3700hZ).

    BAUD - Perhaps the most mis-used term in all of the discussions
    posted in this forum. It actually refers to the unit of measure for
    the number of discrete changes of state which occur in a
    communication channel per second (ie. the number of times per second
    that carrier frequencies are modulated). It is an old term from the
    days of Frequency Shift Keyed modems. The name honors Jean Maurice
    Emile Baudot, who invented a bit encoding scheme for characters (it
    is/was not the same as that presently used for encoding ASCII
    characters however).

    Relative to FSK modems, the use of Baud referred to the rate that
    you could shift from one FSK Tone to another. The tones directly represented the ones and zeros of data being transmitted. In the
    early days they were generally referred to as the Mark Frequency and
    the Space Frequency. Accordingly, with this direct correlation of
    tones to 1s and 0s, the Baud Rate was the same as the Bit Rate.
    [Note: The FSK transmission schemes referenced above are to
    bi-frequency implementations such as V.21 and the Bell 103 protocol. Multi-frequency FSK schemes also exist, but they have not been
    widely implemented over the PSTN].

    As more complex ways of transmission were devised it was natural to
    try to extrapolate this concise definition to define their
    operation. An early extrapolation was to Phase Shift Keyed (PSK)
    modems such as the V.26 Series of modems. This was unfortunate, but
    it did actually occur. The extrapolation went like this: The PSK
    modem generated a signal with 4 possible phase states and thus 4
    possible phase changes. The states were 0, 90, 180 and 270 degrees
    of the carrier. The possible changes were the same.

    ___ MPost/2 v2.0a
    - 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.
    Cheers! Gord
    -=Team OS/2=-
    --- timEd/2 1.10.y2k+
    * Origin: Marsh BBS (c), Dawson Creek, BC Canada (1:17/23.1)