Re: Computer clocks.

Willie Koorts (
Tue, 28 Jul 1998 13:54:44 +0200 (GMT+0200)

On Thu, 23 Jul 1998, Frank Reed wrote:

> Question: does anyone know if there is a standard format for audible time
> codes that would be suitable for this purpose.  Some of the desirable
> attributes of the code would be:
> 1.  A user could easily learn to "understand" the codes as he hears them,
> 2.  User can easily discern time to a resolution of one second or less,
> 3.  Frequent ambiguity resolution.  See explanation below.
> 4.  Recorded audible signal plays back with little degradation.
> By frequent ambiguity resolution, I mean that on playback of a short
> recorded segment of the time code the user can establish the date and time
> when the recording was made.  For example, if the recording was made by a
> voice activated microcassette recorder, each recorded segment may be only a
> few seconds in length - the time code recorded (and discernible on
> playback) within each segment should probably contain enough information so
> the user can determine the minute and second of the hour.  Hour of day, and
> day of year information would be useful as well, but can probably be
> established by other means.

Hi Frank and others

I don't know of an exact code to be recognisable in just a few seconds' 
worth of recording, but with our old time service at work, a crude form 
of coding was used on the sidereal time sounders.  It worked as follows:

Every second was announced by a 10ms burst of 1kHz with the start of the 
burst coinsiding with the start of the second (like WWV).  The ten's of
seconds (10, 20, 30, etc.) had a pip of double the second's lenght - 
a 20ms burst of 1kHz.  The minute change had an even longer burst (500ms 
I think), somewhat like WWV again.  

These all used 1kHz bursts, so coming up with a code using more that one 
frequency (not too many though) might perhaps not be too difficult to be 
recognised within say 10 sec.s.  Any takers?

                        Willie Koorts   

       Cape Town,  Observatory   33d 56' 03"S   18d 28' 36"E   GMT + 2h
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