[GreenKeys] WRU, SELCAL, and other features in TTY-CONNECT

[Eric Scace K3NA]

No need for "QST1" as a bulletin code.  Just send ZCZC as the call director code; i.e., as the 4-character selcal sequence.  See the
example in (2) in my earlier message.

-- Eric K3NA

-----Original Message-----
From: Bob Camp [mailto:ham@cq.nu]
Sent: 2004 April 28 20:09
To: eric@k3na.org
Cc: gil smith; GreenKeys
Subject: Re: [GreenKeys] WRU, SELCAL, and other features in TTY-CONNECT


Hi,

SELCAL id's ... hmmmm

I guess I have always set this up the wrong way. If I'm looking for
B8TQ as a SELCAL I always would look for B8TQ+space of course if we do
that then the end of address code would have to start with a space. I
realize this goes beyond the normal four characters you put in a stunt
box. I've always done it with digital stuff .....

What ever we do your point is well made - we need to be consistent
about it. I always would send the whole call because I could never
remember who is using 3, 4, or 5 characters. It would be a lot easier
if we agreed to do in just one way.

If everything is going to be a uniform four characters long then we
need a four character bulletin code. We could easily use QST1 since
that would never conflict with a call sign derived code.

	Take Care!

		Bob Camp
		KB8TQ


On Apr 27, 2004, at 10:57 PM, Eric Scace K3NA wrote:

> Hi Gil, Bob and everyone --
>
>    I'll try to address the various points that have been raised in
> several messages this evening on the proposals.
>
> 1)  Conditioning code:
>
>    My suggestion was to use the sequence "5 Spaces, 2 CR, LF" as the
> transmitted conditioning code because of its common, historical
> usage.  A big benefit of this sequence is that it puts the following
> call director codes (the sequences that actually select
> stations) on a new line -- very helpful when preparing a message for
> transmission.
>
> 2)  Call Director Code for messages to be copied by all.
>
>    I had suggested "ZCZC".  Others have suggested "QST".  The problem
> with "QST" is that a mechanical system will trigger on "QST"
> whenever it occurs after the Conditioning Code, and before the End Of
> Address sequence.  So now we have a problem if VE3QST (a real
> station!) joins our network.  His 4-character Call Director Code will
> be "3QST".  But anytime someone sends "3QST" after the
> Conditioning Code, EVERYONE will get activated!
>
>    By using a four-character sequence which would be extremely
> unlikely to appear in a radio callsign, such as "ZCZC", we avoid this
> problem.
>
>    Another minor advantage is revealed by examining the current format
> of ARRL bulletins.  Here is an example:
> ZCZC AG14
> QST de W1AW
> ARRL Bulletin 14  ARLB014
>> From ARRL Headquarters
> Newington CT  April 23, 2004
> To all radio amateurs
>
> SB QST ARL ARLB014
> ARLB014 Illinois amateurs support tornado relief, recovery efforts...
>
>    Note that every ARRL bulletin begins with ZCZC.  (The ARRL then
> sends a 4-character code, beginning with "A" for "ARRL", then one
> letter (e.g., "G" for general bulletin, "D" for DX, "P", for
> propagation, and then a 2-digit serial number which starts with 01 at
> the start of the year.  This sequence will not be confused with our
> proposed Call Director Codes based on the least four characters
> of a radio callsign, because radio callsigns almost never end in two
> digits.  Therefore, when someone wants to forward an ARRL
> bulletin to our group, the transmission can start with the
> Conditioning Code, and then immediately continue with the ARRL
> bulletin
> text as sent; everyone who detects ZCZC will receive it.)
>
> 3)  Motor start/stop.
>
>    Motor start/stop are different for mechanical SelCal systems vs.
> silicon-based systems.
>
>    In a mechanical SelCal system, the machine's motor is turned on
> whenever a RTTY signal appears on frequency.  The motor runs (and
> a Model 28 will continue to make little snickety noises as it decodes
> every transmitted character) throughout every transmission --
> even transmissions which are not directed for that station.  A Model
> 28 runs in print-suppression mode until a Conditioning Code,
> followed by that station's Call Director Code(s (specific and/or
> all-stations), has been detected.  The motor does NOT turn off at
> the End of Message or End of Address sequence, since another message
> may follow which must be examined for relevant Call Director
> Codes.  The motor turns off only when the RTTY signal disappears from
> the frequency.
>
>    Some machines had an internal mechanical time-out mechanism that
> run whenever an all-mark condition was maintained on a circuit
> for 20-30 seconds.  If no characters were detected (i.e., the loop
> current never dropped or reversed polarity), the machine would
> shut down after this mechanical time-out.  Whenever loop current was
> interrupted (or polarity reversed, on polar loops), the motor
> was immediately turned back on.
>
>    In a silicon-based SelCal system, some wear and tear on the machine
> can be avoided.  The silicon-based logic (TTY-Connect, for
> example) can delay turning on the machine's motor until the
> Conditioning Code followed by the desired Call Director Code(s) has
> been
> detected.  In this case, it is perfectly appropriate for the
> silicon-based logic to turn the machine's motor off after the End of
> Message sequence ("NNNN") has been detected.  If a subsequent message
> to the same station follows, the silicon-based logic can turn
> the motor back on after the Call Director Code has been detected at
> the start of the subsequent message.  Therefore, a "motor off"
> code sequence is NOT needed.
>
>    Motors actually spin up to speed fastest if NO characters are being
> sent during their start up.  So, in a silicon-based system
> with some buffering, I would start the motor with loop current on (all
> mark condition) and give it a few hundred milliseconds to get
> up to speed, and only then start feeding characters to the machine.
>
>    Similarly, the mark condition should be held while the motor is
> shut down... and maintained while the motor is off.  If you drop
> the loop current while a machine is shut down, the selector magnet
> will trip.  When the motor starts up again, the selector
> mechanism will rotate through and a character may be printed on the
> paper.
>
> 4)  Auto CR LF insertion.
>
>    This is a convenient function.  Model 28 machines could be set up
> mechanically to jump down to a new line if more than "x"
> characters were received; typically 73-80.  But other teleprinter
> machines didn't have this system.
>
>    My recommendation would be to insert CR CR LF and either one Figs
> or one Ltrs, depending on the case for the next printing
> character.
>
>    I would recommend against inserting a "\" character.  That
> character doesn't exist in ITA2 (5-bit) code.  As a philosophical
> point, I am biased to make minimal modifications to the message in
> progress.  The principal purpose of the Auto CR LF function is to
> keep a mechanical machine from piling up characters at the right edge
> of the paper because a garble wiped out the original CR LF
> transmission.
>
> 5)  Why is an End of Address sequence needed?
>
>    The EOA sequence works together with the Conditioning Code to
> indicate when Call Director Codes are being sent.  Without an EOA
> sequence, the contents of a message may cause other stations to start
> copying the message when they were not intended recipients.
> Take this example:
> [carrier on] DE N6JP  <<-- legal ID
> 12 Ltrs 5 SP CR CR LF LTRS LTRS <<-- contains the Conditioning Code
> B8TQ  <<--- no EOA code defined, so everyone's system keeps looking
> for call director codes!
> HI BOB.  DID YOU SEE ERIC'S MOST RECENT MESSAGE?  K3NA IS REALLY BEING
> A JERK ABOUT THE NEED FOR END OF ADDRESS CODES.  BYE FOR NOW.
> CR CR LF LF LF LF NNNN 12 Ltrs [followed by legal ID and carrier off]
>
>    Notice that in this example, since no EOA was defined, the letter
> sequence "K3NA" in the middle of the message text will cause
> K3NA's machine to turn on -- just in time to receive an unflattering
> comment - hi!
>
>    I had proposed that CR CR LF, sent after all the Call Director
> Codes, could be the EOA sequence.  That keeps all the Call
> Director Codes on their own line, separate from the message text.
> Someone else's message earlier today contained an interesting
> idea: the sequence "Space DE Space" would be a nice EOA sequence
> because it allows us to move the legal ID of the sending station to
> the end of the line with the Call Director Codes.  For example:
> [carrier on]
> 12 Ltrs 5 SP CR CR LF LTRS LTRS <<-- contains the Conditioning Code
> B8TQ DE N6JP  <<--- KB8TQ's Call Director Code followed by EOA and
> transmitting station ID.
> [ continue with message...]
>
>    Here the " DE N6JP" contains the EOA sequence I just described and
> the transmitting station's callsign.
>
>    Note that the sequence must be four characters including the
> preceding space.  Defining the three-character sequence as "DE
> Space" won't work -- it will get triggered whenever anyone attempts to
> send a message to K8DE (for example).  It may be less likely
> that DE4N would join our network, so "Space DE" could be a
> three-character EOA sequence, if it was important to keep the EOA
> sequence to a minimum.
>
> 6)  Using a complete callsign as a Call Director Code
>
>    This is a bad idea because it has unintended consequences when
> calls contain more than four characters.  For example, assume that
> KK6XX is part of our network.  If someone sends "KK6XX" at the point
> where Call Director Codes are expected, this can also be
> accepted by K6XX and KK6X as their code, too!   Similarly "KB8TQ" will
> turn on KB8T's station as well as KB8TQ.  While one could
> play the percentages and hope that two stations with this kind of
> conflict don't join the network, it is a weak design.
>
> ==========
>
>    I hope this is clear and helps.  Feel free to call me
> (617-712-1523) if that would be easier.
>
> 73,
>     -- Eric K3NA
>
>