[time-nuts] Encoded 1PPS signals

[Clayton G]

Hi Nuts,

I have been building an LF transmitter, and have provision for a 1PPS input 
for calibration purposes. However I would like to be able to provide more 
time information than just the second pulses. It occurs to me that full time 
info could be encoded onto a 1PPS stream by changing the width of the pulse 
itself. The rising edge can be left unchanged to indicate the precise 
second, but the trailing edge can vary between (say) 100mSec and 300mSec, 
and this could encode 60 bits (with suitable idle pulses etc for 
synchronisation) in each minute. Using this I could encode full date and 
time into the 1PPS stream.

My question is, does such a standard already exist, or has anyone developed 
something along this line?
If no, I plan to implement something suitable myself, and will publish it 
should it be useful to others.

Regards
  Clayton
  (VK1TKA)