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<div class="moz-cite-prefix">On 13/04/16 23:34, Clem Cole wrote:<br>
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<div class="gmail_quote">On Tue, Apr 12, 2016 at 11:14 PM, Tom
Morris <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:tfmorris@gmail.com" target="_blank">tfmorris@gmail.com</a>></span>
wrote:<br>
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<div class="gmail_quote"><span class="">On Wed, Apr
13, 2016 at 12:28 AM, Clem Cole <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:clemc@ccc.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:clemc@ccc.com">clemc@ccc.com</a></a>></span>
wrote:<br>
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Hang on -- BREAK is not in the old USASCII
7 bit map. As explained in RFC 854, it
was a >>key<< on the old
Teletype ASR33 (and the ATTEN key on the
IBM 2741). What BREAK did was sent a
very long (i.e. 1 second if I remember
correctly) "marking" time signal.</div>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">Bad
wording -- sorry see below...</div>
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I don't remember using an Asynch terminal without a Break key,
though my Hitachi Peach lacked one, despite the terminal emulator
as ROM Basic statement.<br>
HP 3000 programs that didn't trim trailing blanks in output lines
were reviled over a 300 baud acoustic coupler.<br>
<br>
Reading the MSKermit source and the DOS Encyclopedia, Kermit sends
either a 275 ms break or a 1.8 s long break.<br>
This is done by turning on the BREAK state (SETBRK) in the 8250 Line
Control Register, pausing for the period and <br>
turning it back off again. I'd expect other terminal emulators to be
doing something similar.<br>
<br>
Reading the DosBox code, the NullModem serial case isn't checking
for a Telnet connection, instead doing<br>
I don't<br>
nullmodem.cpp:/* setBreak(val) switches break on or
off **/<br>
nullmodem.cpp-/*****************************************************************************/<br>
nullmodem.cpp-<br>
nullmodem.cpp:void CNullModem::setBreak (bool /*value*/) {<br>
nullmodem.cpp- CNullModem::setRTSDTR(getRTS(), getDTR());<br>
nullmodem.cpp-}<br>
<br>
So it should be easy to just send the Telnet break command when
Break is turned on when telnet connected.<br>
If so DosBox could be useful for running terminal emulators for
SIMH.<br>
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<div>Definitely not an ASCII character,</div>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">That was
my point.... I'm glad you agree.</div>
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<div> but where would an ancient electromechanical
device like the ASR-33 have kept this fancy 1
second timing logic?<br>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">That's
non-sense. Timing on electromechanical devices was
gears, cams et al. The teletypes had plenty of them.
How BREAK was implemented on the terminal is not
relevant to the conversation, but >>what<<
is being sent its and how to do same function with
todays tools.</div>
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<div>I'm pretty sure that the length of the break is
whatever length you could be bothered to hold the
key (and thus the line) down.</div>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">I dp
believe you are correct on this. I'd have to go find
the old documents, but BREAK was defined in one of the
communications standards. IIRC correctly it is as N
character times of marking time. Where N was defined
as a large number - in order of seconds not small
sub-seconds.</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">Again if
I recall correctly, BREAK is an concept that came from
the morse code world and was inherited as transmission
standards changed over the next 100 yrs.</div>
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<div> It was only in much later models of terminals
that logic got introduced between the BREAK key
and the line.</div>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">I'll take
you word on it and I do believe you are correct, I've
forgotten and no longer have access to service manuals in
my own archives.</div>
<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif"><br>
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<div class="gmail_default"
style="font-family:arial,helvetica,sans-serif">But it goes
back to my point about what was being generated then, how
to generate it today.</div>
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