[GreenKeys] WRU and SELCAL

Mon, 26 Apr 2004 19:57:35 -0400

Hi

About the only thing I would add would be to substitute CR LF LTRS in 
the places you show CR LF combinations. If we are going to be 
compatible with a wide variety of machines (including pre model 15's 
and even Creeds) padding the CR is going to be an important part of the 
system. Of course CR CR LF LTRS or CR CR LF LTRS LTRS may be needed if 
we go far enough back in time ....

	Take Care!

		Bob Camp
		KB8TQ

On Apr 26, 2004, at 9:59 AM, Eric Scace K3NA wrote:

>    Suggestions:
>
> 1)  Stick to "NNNN" (four "N") as the standard turn-off sequence, but 
> programming the SelCal system to turn off on receipt of 3 Ns.
> This takes one less slot in a stunt box.  This has work successfully 
> for decades on commercial and military RTTY circuits.
>
> 2)  No need for double-LF in the sequences.
>
> 3)  Why use [callsign]ZW for the WRU interrogation?  What was wrong 
> with the traditional "[callsign]Figs H Ltrs" followed by
> immediate drop of carrier?  The stuntbox would be set to respond upon 
> receipt of [call] Figs H; the Ltrs was used as a buffer to
> compensate for mechanical lag.  (See page 17 of the "Teletype Model 28 
> Stuntbox" booklet.)
>
> 4)  Given the scarcity of function bars, latches, forks, pawls, 
> levers, etc., perhaps we could agree to use the last 4 characters of
> a callsign as the actual selection sequence.  For four-character calls 
> like "K3NA", this amounts to a full call.  But for "WB3ABC",
> "3ABC" would be the sequence encoded into the stuntbox or its 
> electronic equivalent.  The cases of overlapping 4-character sequences
> would be rare.
>
> 5)  A complete SelCal system needs to define:
>    -- "conditioning code": the sequence of characters used to alert 
> machines that call-directing codes are to follow.  Upon receipt,
> a machine is in the 'select non-print' state.
>    -- "call directing code" (CDC): this is what selects a machine to 
> receive the message.  Selected machines switch to the 'select
> print' state.
>    -- "end of address code": this tells machines that all CDCs have 
> been sent; if the machine hasn't been selected yet, it need not
> pay attention to the message.  All non-selected machines move to the 
> 'non-select' state and don't pay any attention to anything else
> until the next conditioning code is heard.
>    -- "end of message code" (EOM): this tells machines that were 
> selected that the message has been completed.  They can move to the
> 'non-select' state now.
>
>    An example of a commonly used approach:
>
>    conditioning code: twelve LTRS, five SP, CR CR LF.  Note that 
> normal message text would be unlikely to send a sequence of spaces
> followed by a CR.  The stuntbox might be encoded to use just four or 
> three spaces, followed by one CR, to actually put the machine
> in the 'select non-print' state.  The twelve LTRS are sent to allow 
> all the machines to get synchronized.
>
>    call directing code: last four characters of a callsign, or ZCZC 
> (selects everyone).
>
>    end of address code: CR CR LF.  Detection of CR CR or CR LF should 
> be sufficient to put unselected machines into the non-select
> state.  For reasons discussed below, Figs H must also be interpreted 
> as an end-of-address code.
>
>    end of message code: NNNN.  Detection of NNN should be sufficient 
> to put a selected machine into the non-select state.
>
> 6)  If the above definitions are used, the WRU function can be:
>    12 Ltrs, 5 SP, CR CR LF Ltrs K Figs 3 Ltrs N A Figs H Ltrs (drop 
> carrier).
> This uses the conditioning code, CDC, and Figs-H as a 
> WRU/end-of-address code.  For the called station, Figs-H triggers the 
> WRU
> response.  For the other stations, Figs-H places their machines in the 
> non-select state because their CDC did not immediately
> precede the Figs H.
>
>    As I recall, in the Model 28 world the WRU response was generated 
> by a drum encoded with the response.  I don't remember the
> number of characters available on the drum, but it should be enough to 
> send some number of Ltrs, CR CR LF DE [callsign].  The drum
> clicked on right away after Figs-H was received.
>
> ========
>
>    Of course all of this can be imitated by computers or other 
> electronic controllers.  I detect that one of the desires of the
> community is to use sequences which can be handled by traditional 
> machines as well, which is why I made the above suggestions.
>
>    -- Eric K3NA
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Roy Norris
> Sent: 2004 April 26 00:58
> To: [email protected]
> Subject: [GreenKeys] WRU and SELCAL
>
>
>
> I have been searching the internet and old issues of RTTY Journal
> looking for suitable designs for a WRU (answerback) and SELCAL design
> that would serve our purposes for an auto start net.  While this could
> be done on a PC, my thought is that most would not want to keep a PC
> running continuously to provide that function.  WRU and SELCAL 
> functions
> can be provided in a model 28 stunt box arrangement however that
> approach would require leaving the TTY machine on or the use of an
> analog/TU  based autostart which are notoriously sensitive to false
> triggers by noise or off frequency signals and carriers.
>
> It seems to me that an ideal solution would be an external,
> microcontroller based box connected to the TU via an RS-232 port that
> would provide the following functions:
>
> 1.	PROVIDE DIGITAL AUTOSTART.  - monitor the RS-232 output of the
> TU and when a valid digital signal is present, close a relay that would
> turn on the teletype machine. Turn off the teletype machine when an
> "NNNN" is detected.
> 2.	PROVIDE WRU CAPABILITY - monitor the RS-232 output of the TU and
> when either the sequence "ZCZC"  or (callsign)ZW was received, close a
> relay which would key the push-to-talk switch on a transceiver and send
> the following string to the TU
>     : " (20 diddles)(CR)(CR)(LF)(LF)(LTRS)(LTRS) DE (Callsign), (name),
> in (location) (CR)(CR)(LF)(LF)(LTRS) NNNNN (CR)(CR)(LF)(LF)(LTRS)",
>      followed by turning off the relay which had activated the
> push-to-talk switch.
> 3.	PROVIDE MULTIPLE SELCAL - monitor the RS-232 output of the TU
> and when any of several individually selectable code sequences were
> received, close a relay      that turns on the teletype machine.
> Monitor for "NNNN" and turn off the relay that operates the TTY machine
> when received.  Codes would include a) ones for receiving a message
> directed at that particular station (possibly use the station callsign
> as a selcal trigger). b) a code for receiving bullitiens  c) a code for
> receiving "all-calls"..  Each code would be individually activated by a
> front panel switch so that an operator could choose to receive or not
> receive messages addressed to his station, messages that were 
> bulletins,
> messages that were "all-calls".
>
> All of this capability has been incorporated in various devices in the
> past so there is nothing new here.  I don't recall seeing it available
> all in one external unit.
>
> IIt would be wonderful if this capability could be incorporated in the
> TTY Connect project currently underway by Gil Smith.  I believe he has
> made provisions for an optional microcontroller on the board he is
> developing but I am not sure the board is designed so that it could
> provide these functions.  (What say, Gil??)  Alternative, a small
> inexpensive stand alone box could be designed using a microcontroller.
> If there is anyone on GreenKeys that has the necessary skills and would
> be willing to undertake the project, please speak up.
>
> Alternatively, I will try and do it myself, although it has been 20
> years since I did any programming of this nature and it was on 8085
> computers, not microcontrollers.  But I guess I could get back up to
> speed in a couple of months.  It would be tremendously helpful if I
> could locate any of IRV Hoff's source code for his RMON program or his
> standard teletype program that was use on the 20 meter autostart
> frequency of 14.0875 Mhz.  Does anyone on the list have this or have an
> idea of where I might find it??
>
> I have looked at the aforementioned RTTY12 program.  It is written in
> Basic and has selcal but no WRU that I can find.  Irv Hoff's code would
> be the best if we can find it.  I hate that I threw away my copies some
> years ago.
>
> Thoughts?  Suggestiohns ??  Ideas, pro and con ??
>
> Best regards - Roy Norris, K4EEG
>
>
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