Ian Batten igb at batten.eu.org
Fri Sep 3 17:16:44 EDT 2010

On 3 Sep 2010, at 20:19, M. Warner Losh wrote:


> I think that this is why the leap second proposals say they won't

> disseminate DUT1 anymore. All they really mean by that, I think, is

> that we'll measure it, we'll pubish it, but the time broadcasts will

> reset it to '0' and users should note that it isn't available that way

> anymore.

I suspect that system that are consuming DUT1 are not exactly at the
thrusting forefront of modern development. So a piece of equipment
that consumes DUT1 from MSF (and we can only speculate about what that
equipment might be) could be of an arbitrary age, and could well be
operating on autopilot with several iterations (or even generations)
of staff having passed. I don't know when the current format was
agreed , but Wikipedia implies 1967.

So "users should note" is an interesting concept. Firstly, it's not
clear how you'd tell them: even BBC1 running idents saying "Next,
Eastenders, but first an announcement for people who have equipment
that consumes DUT1" may not work, as people may not realise the
equipment they're using is included. And secondly, as it's most
likely that equipment is consuming DUT1 to do something astro-y,
rather than just displaying for decoration, even if people can be
told, quite what are they expected to do about it?

Secondly, there may be systems that don't bother to process DUT1, but
nonetheless rely on its being <1s. For example, astro-navigation is
still taught, and I suspect that although 1s doesn't matter, 10s might
(someone who's used a sextant in anger can tell us the precisions that
are normal). Obviously, the correction can be supplied out of band,
but all those mechanisms will need to be set up.


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