= 21,600 seconds / 6 seconds 

 = 3600. 



Discrete data: 



It is more difficult to detect errors in the discrete dive 

 information. However, the following checks can still be performed: 



1) Does the failsafe field have a zero value? Since the conditions 

 for a non-zero value of the failsafe field were never attained, 

 any non-zero value in this field is an error. 



2) Is the temperature above -40 degrees C? This check is separate 

 from the following temperature check, because transmissions from 

 one of the tags would occasionally report a drop to an extremely 

 low temperature (below -40) and stay at that reading for an 

 extended duration (up to a couple days). During these times, all 

 the other readings would appear normal. Therefore, we concluded 

 that the sensor, rather than the transmission, was faulty. 



3) Is the temperature within believable limits (3 - 36 degrees C)? 



4) Is the duration of the dive just previous to the transmission less 

 than a maximum value (45 minutes)? 



5) Is the inter-transmission dive count less than the maximum 

 possible for the repetition period? With a minimum dive duration 

 of 6 seconds and a minimum of one second at the surface, the 

 minimum duration for a full dive-surface cycle is 7 seconds. If 

 the repetition period is 42 seconds, a maximum of 6 dives can 

 occur during the repetition period. 



6) Is the sum of the previous dive duration and the minimum time 

 necessary inter-transmission dives (7 seconds per inter- 

 transmission dive) less than the duration of the interval between 

 the currant and previous transmissions. 



Examples: 



previous 



dive inter calc actual 



duration trans interval interval error 



HH:MM:SS dives HH:MM:SS HH:MM:SS 



00:50:00 0:50:00 1:30:00 actual exceeds maximum 



00:02:00 0:02:00 0:01:30 calc exceeds actual 



00:02:00 2 0:02:14 0:02:10 calc exceeds actual 



00:02:00 2 0:02:14 0:02:20 no error 



If the dive duration is zero, is the inter-transmission dive count 

 zero? A dive duration of zero occurs when the tag is out of the 

 water for the entire repetition period. In this instance, no 



157 



