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

[Bob Camp]

Hi,

There are several codes needed:

1) Something that comes as a SELCAL in front of all net traffic. If I 
want to copy all the net I set that up to fire up the print mechanism. 
It also acts as the "turn on" code for digital motor control. ZCZC is 
the obvious candidate.

2) Everybody needs their own SELCAL and we need to be consistent about 
how many characters are in it.

3) We need an end of message code - NNNN is the obvious choice. If you 
started up with your code then NNNN stops printing.

We *may* want to have a couple more codes defined. If we send them and 
they are not recognized nobody is hurt.

1) Since ZCZC is already taken we need a "message for everybody" code. 
Weather you call it a bulletin or what ever, you need it to wake up 
those who are not copying the whole net. If we are going to use it we 
need to agree on a code.

2) How about an end of transmission code? NNNN is nice for messages but 
if you started up on ZCZC you would not shut down at the end of each 
message. CZCZ would be fine with me unless that makes for a problem.

3) My personal favorite - the ascii art code. I can remember nothing 
that ever brought up as much debate as big picture transmissions. A 
number of people loved them and set up tape punches specifically to 
copy them. They needed the code to turn on the punch. Others hated them 
and wanted the code to shut everything down. Either way it's a handy 
code to have if we are going to do pictures ...

I don't want to beat this to death. I would like to get a reasonable 
discussion of the pros and cons before the software gets written.

	Take Care!

		Bob Camp
		KB8TQ




On Apr 28, 2004, at 8:15 PM, Eric Scace K3NA wrote:

> 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
>>
>>
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