452 



MECHANICAL AND ACOUSTICAL SENSES 



Figure 19 Circuit for a digital release-timing mechanism for detachment of 

 transmitter at a predetermined time. The CMOS, R/C oscillator shown provides 

 accuracies to approx. 20 s/day. If greater accuracies to within 1 s/day are required, 

 a quartz-crystal oscillator may be substituted. Switch S3 provides (counter- 

 clockwise from top) times of IX, 3X, 5X, 7X, 9X, llX, and 13X the input interval 

 at pin 14 of the CD4022. Considerable time adjustment is available via Rl; if this is 

 sufficient, then CD4022 and S3 may be deleted and pin 3 of CD4020 connected 

 directly to Dl. Other counter combinations may be substituted if desired. 



Rl. Frequency control for R/C oscillator 



Dl. 1N914 



D2. 1N4001 



SCR. 2N5060 



LED. MV50. Provides visual indication of operation, can be omitted if desired. 



As shown, LED consumes about 0.8 mA. 

 Si. Power switch 



52. Counter-reset switch. To reset, momentarily throw to opposite position, 

 then return to position shown. 



53. Rotary time-selector switch 



A. Attachment point for breakaway wire (wire in seawater) 



B. Metal plate electrode (in seawater) 



complexity, necessity to use attachments compatible with release, and 

 greater package size and drag, especially if flotation is needed. In general, 

 validity of data is the most important consideration, particularly for long- 

 term trackings involving many days of boat and personnel time. If there is 

 reason to suspect that a recovery-compatible attachment (e.g., external with 

 float) would substantially affect the animal's behavior, then it would nor- 

 mally not be used. If, however, cost considerations severely limit the number 

 of units available, the benefits to the whole study of repeated use of re- 

 covered transmitters might outweight the detriments of the recovery 

 package. 



Data Recording, Reduction, and Analysis 



The simplest way to decode telemetered sensor data is to manually time the 

 pulse rate with a stopwatch. This is easily done in the boat, and usually 



