Jon Romney has sent me a note pointing out a couple of typographical errors in the 16 July draft I distributed, plus illuminating a defect that needs to be fixed.  As you can read in Jon's note, the comments allowing non-binary speed-up/slowdown reproduce rates are not fully consistent with the rest of the specification.  Jon and I discussed this issue at some length and decided that removing any mention of non-binary speed-up/slowdown factors from the specification is the prudent and expeditious thing to do at this time.  This does not preclude such non-binary factors, but does not fully specify how they are to be implemented.  This allows us to finalize version 1.0 of the spec, and we can then discuss the details of non-binary speed-up factors for inclusion in a later revision.  I hope that you find this a satisfactory solution.   I am including the updated specification with this note.  Jon has separately already reviewed and approved this updated version.  Please let me know ASAP if you have any objections to this procedure or the updated draft.  If there are no objections, I plan to notify GVWG and IVS of the completion of VSI-H revision 1 on 7 Aug when I return from travel.

Regards and thanks, Alan


The following revisions have been made to the 16 July draft:

1. p.8, 8.1.2, Note 2: remove specific mention of frequencies (redundant with Table 2)

2. p.11, Table 1: 'Dynamic variability...'

3. p. 12, Table 12: 'Dynamic variability...'

4. p. 13, Table 6, R1PPS comment: change as you suggested

5. p. 13, Table 6 note 1: Remove sentence 'No limits...'

6. Fixed typographical errors you pointed out.

7. Changed 'History and Acknowledgements' to 'Prologue'


At 08:21 PM 7/20/00, Jon Romney wrote:

Dear Alan,


I'm very pleased to endorse the "latest final" version (dated 16 July 2000)

of the VSI-H specification for the first issue of this document.


In doing a final perusal, I did note a few points I'd like to bring to your

attention, but I hope these are either so minor they can be corrected with-

out another iteration through the committee, or can perhaps be saved for

future consideration.


Two are just typographical or editing errors --


--  The first sentence of Note 1 at the top of p. 12 mangles the verb tense

or mood: "... intended for systems where the station 1PPS coming from ...".

The "coming from" should be "comes from", or "is coming from", or maybe "is

provided by".


--  The next-to-last sentence of Section 14.4 on p. 22 includes a superflu-

ous "it" just preceding "QVALID".  Perhaps this should be "the".


A somewhat more substantive problem occurs in Section 10.4, Table 6, on p.

13.  The comment for R1PPS, explaining its relation to DPS1PPS, does des-

cribe speedup (and slowdown) as we currently use it on the VLBA.  But I

thought we were going to permit arbitrary, non-power-of-two, non-integral,

speedup/slowdown factors.  Note 1 just below the table, does say "No limits

are placed on speed-up or slow-down factors.", but the comment in the table

is inconsistent with this.  I suggest a substitute comment for R1PPS, one

which will be consistent with the note: "Ratio of R1PPS to DPS1PPS pulse

frequencies depends on DOM speedup factor."


Only while typing up the preceding comments did I notice the inconsistent

use of embedded hyphens in this part of the document, sometimes "speedup",

elsewhere "speed-up".  A global find-and-replace in your source text to

make one or the other universal would be a good idea.


I gave George Peck a copy of your latest version.  He will send you separ-

ately any comment he has, by the end of the day tomorrow (Friday).


I presume you know that Richard Schilizzi has a report on the VSI-H spec

on his agenda for the GVWG meeting in Manchester next month.  I told him

I'd attempt to fill in for you if you couldn't make such a presentation

yourself, and since I see my name on his latest agenda I suppose you won't

be there.  If this is the case, may I ask you what you would like me to

emphasize in this presentation?  It will be one of eight items that must

all fit into 1.5 hours, so only a few highlights can be covered.  Also,

do you have any visual materials that might be useful for such a talk?


Best wishes,