STUDY OF FREE-RANGING SHARKS 



433 



D3 



(4 13 12 II 10 9 8 



ICM 7213 

 12 3 4 5 6 7 



2.0-6. OV 

 BATTERY 



HOI" 



a. 



XTAL 2 

 C5 



C1 



Rl/ ±R2 

 D1-r -fD2 



J_ 



r~r^t 



16 15 14 13 12 11 10 9 



KD 502 

 I 2 3 4 5 6 7 8 



I XTAL 1 1 



° 4 1K 

 R5 



R3 



C2: 



C3 



-=- 5.6 -8.4V 

 BATTERY 



Figure 7 A sensor-compatible timefix version of the CSU.LB Mark V ultrasonic 

 transmitter (see Figure 4 for more circuit details). Sensor data encoded as the interval 

 between the timefix pulse (one/sec) and a sensor pulse following it by 200 to 400 msec 

 (thereby distinguishable from it). The ICM7213 (Intersil, Inc.) is a CMOS precision clock 

 oscillator/divider with a 1-Hz output. It's separate battery minimizes power drain (100 

 Id A at 3.0V); if this not needed, the entire transmitter can operate from a single suitable 

 supply, e.g., 5.6V. 



In the circuit shown, Rl is the sensor (range chosen to give 200-400 msec interval), 

 and R2 is much higher, e.g., 2M. In this mode, the minimum length of the timefix pulse is 

 determined by the length of the clock output pulse (7.8 msec). Both timefix and sensor 

 pulse lengths are increased by upward adjustment of R3, but the timefix pulse will be 

 longer by about 7.8 msec. 



To operate as a simple timefix unit (without sensor), leave pin 15 open and eliminate 

 Rl, R2, Dl, D2, and D3 and its connection. Pulse length is controllable above 7.8 msec 

 by R3. 



C4, C5. Clock-timing capacitors (approx. 10-30 pf each) 

 XTAL 2. Clock crystal (A-T quartz, 4.194304 MHz) 

 Dl, D2, D3, D4. 1N914 



would effectively increase the signal-to-noise ratio, thereby improving recep- 

 tion under certain conditions. 



Data Storage— The capacity to store sensor data would be a very 

 valuable addition to the transmitter package for many studies, particularly 

 long-term ones. A small memory circuit permitting remote interrogation 

 would hold a very useful amount of data but not nearly the quantity that 

 the transmitter could produce in 24 h. Thus, while full detail (sensor read- 

 outs several times a second) can be obtained only by continuous recording, 

 this amount of detail may not be necessary for many research objectives. 

 If, for instance, the researcher is interested in a shark's general day-night 

 activity pattern, it may suffice to know its mean swimming speed for each of 

 the 24 h. Even more could be learned if an upper and lower range value 



