Re: Purpose of txtail ?

From: Jens David (kvindp@rele.tunk.net)
Date: Wed Feb 02 2000 - 19:27:50 EET

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    > On Tue, 1 Feb 2000, Jens David wrote:
    > > John Ackermann wrote:
    > > > Not all hardware implementations need it, but there are at least some systems
    > > > where dropping the PTT immediately results in the tail end of the packet
    > > > (including the CRC and closing flag) to be chopped off.
    > >
    > > In fact per definition the txtail starts after the closing flag has been sent.
    > > Usually itīs the modem which causes some delay on the signal. Consider for
    > > example the scrambler or the FIR filter on a G3RUH-compatible modem.
    > >
    > So .. ok .. txtail is important. Couldn't we use some fixed (or computed)
    > value which couldn't be mis-configured ?
    > (driver/baudrate/anything dependant)

    Yes and no. With current available modem designs sure. But not with a future
    modem which does for example a convolutional FEC with long interleaver.

      -- Jens



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