[ntp:questions] Re: What went wrong with the leap second

Rob van der Putten rob at sput.nl
Thu Jan 5 09:54:43 UTC 2006

Hi there

"David L. Mills" wrote:

> Here is how I tested the leapsecond code. You may notice in ntp-dev/util
> a tg.c program. It generates fake IRIG and WWV/H audio signals that can
> be piped out of one machine and into another. The code and options are
> documented in the source file. When started without a time of day
> argument, it uses the time from the system clock, but this can be
> changed by an option. An option can be used to insert a leap second in
> the audio stream and to light the leap warning; however, the IRIG format
> has no provisions for that, so it works only for the WWV/H signal.
> To see that the kernel follows the leap, use the WWV/H signal and set
> the time option to fifteen minutes before midnight UTC on the last day
> of June or December The fifteen minutes gives time for the WWV/H driver
> to lock up. To see what happens if the kernel is not equipped for leap
> insertion, disable the kernel (disable kernel) from the configuration file.
> In all the testing with this thing, I never got unexpected behavior, but
> since lots of others did experience pinball machine behavior, some wee
> thing must have been overlooked. Workin' on it.

One would have to test the hardware to.
A fake DCF77 isn't that hard to create.
With GPS this is probably much more difficult.

Maybe the cause of all the trouble is the availability of cheap but broken
GPS receivers.

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