STUDY OF FREE-RANGING SHARKS 427 



Single-Channel (One Sensor)— In recent years, biologists have been 

 increasingly interested in including one or more sensors in the transmitter 

 package, so as to obtain data parameters in addition to the animal's location. 

 In many UST circuits, replacing one fixed resistor with a resistor that varies 

 with the desired parameter converts a location-only unit into a one-channel 

 data transmitter. A simple example is the incorporation of a thermistor that 

 causes the transmitter to change pulse rate with temperature. When data are 

 encoded as pulse rate, identification of individual USTs must be done by 

 other means, usually frequency differences. 



To telemeter sensor data accurately, the transmitter circuit itself must 

 have high pulse-rate stability over the expected range of battery voltages and 

 environmental variables. Thus, the degree of stability adequate for a simple 

 pinger may be inadequate for a unit used to telemeter sensor data. For 

 example, the Mark V shark transmitter (Figure 4) was specifically designed 



Figure 4 Circuit of the CSULB Mark V ultrasonic transmitters using CMOS digital 

 integrated circuits, quartz -crystal frequency control, and hybrid thick-film construction. 

 Basic transmitter components are in one hybrid (Keldron KD502), the multiplexer (mux) 

 is in another hybrid (KD533), and some additional parts remain external for parameter 

 adjustment, etc. For operation as a pinger (no sensor), omit KD533 and use a fixed 

 resistor in place of Rl and R2. For single-channel operation, omit KD533 and use the 

 sensor at Rl. For multichannel operation (rapid-mux format), remove Rl and use the 

 sensors and/or fixed resistors at R6-R12. For multichannel operation (slow-mux format), 

 separate the multiplexer from the main transmitter at point C and, instead, drive the mux 

 clock input (at point C) with a separate clock oscillator at the desired switching rate. 



Rl. Pulse-rate control. The sensor in single-channel operation; unaffected by 



battery voltage (approx. 50-300 k; 150 k = 2.2/s, 300 k = 1.2/s). 

 R2. Fail-safe resistor. If desired, to ensure continued operation if the sensor fails 



by opening circuit (approx. 1-2 m). 

 R3. Pulse length control (approx. 560 k = 10 ms, 270 k = 5 ms; pulse lengths 



increase somewhat as voltage decreases). 

 R4. Power-limiting resistor. If desired, to limit the current to the power 



amplifier to extend battery life (few ohms-few tens of ohms). 

 R5. Reference-channel resistor for multichannel operation (chosen to be lower 



in resistance than any possible sensor value). 

 R6-R12. The sensors for multichannel operation, i.e., the seven data channels. 

 CI. Pulse-rate control (approx. 1.0 /J.F tantalum). 



C2. Logic power boost (approx. 120-juF tantalum). 



C3. Main power boost (approx. 360-510 |UF tantalum). 



XTAL. Statek SX-1H (various frequencies near 40 kHz). 

 Ql, Q2. Darlington power transistors (GE D40C1 or pairs of 2N2222's). 

 Tl. Primary, 80T CT #32; secondary 93T #34 (Ferroxcube 1408PL003B7). 



LI. 92T #36 (Ferroxcube 1 107CA2503B7 ). 



PZT. Thin-walled cylinder of PZT-4. OD 22.2 mm (0.875 in.); ID 19.8 mm 



(0.780 in.); height 12.7 mm (0.5 in.). 



All capacitors in microfarads; all diodes, 1N914. 



For external triggering of an output pulse (as in some timefix or transponding 

 operations), apply a logic low at point D. The minimum pulse length will be the length 

 of the externally applied low. Additional pulse length is obtained by upward adjustment 

 of R3. 



