[time-nuts] 1pps; what good is it?

[Hal Murray]

> It also has a 1 pulse per second output; what is it good
> for, in industry, and for me?

That 1 PPS signal ticks on the UTC second boundary.  That lets you transfer 
accurate time as well as frequency to other boxes.

Suppose you want to build a time server.  If you connect up the serial port, 
you can ask the Z3801A what time it is.  The answer won't be very accurate 
(few ms) because of delays in the serial port hardware and software.  With a 
PPS signal (and widely available patches to the OS) you can get that down to 
microseconds.

The PPS signal alone doesn't tell you which second a pulse corresponds to.  
You need to know the time within a fraction of a second by some other means 
such as the serial port.


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