Re: Computer clocks.

Willie Koorts (wpk@saao.ac.za)
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?

Cheers
Willie
                        Willie Koorts   wpk@saao.ac.za   

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