will minimize the equivalent sound-pressure spectrum 

 levels of the maximum system noise of the hydrophone- 

 preamplifier combination (see section 2. 6. 3). The selected 

 characteristics shall be stated by the supplier. 



2. 3 Preamplifier. 



2. 3. 1 Input Resistance. Not less than 100 megohms. 



2. 3.2 Input Capacitance. Not more than 30 picofarads. 



2. 3. 3 Voltage Gain . 30 dB ±1 dB. 



2.3.4 Output Impedance. Not more than 50 ohms. 



2.3.5 Open-circuit Output Voltage, Maximum. Not 

 less than 2 V rms, 5 V peak-to-peak. 



2. 3. 6 Power Supply. Not more than 5 mA. @ 10 - 14 

 Vdc. [Changed to 12 mA to accommodate added output 

 stage. ] 



2. 3. 7 Calibrate Resistor. 10 ohms ± 0. 1 ohm. 



2.4 Case . 



The case for housing the hydrophone and preamplifier shall 

 be cylindrical in shape with rounded ends approximating a 

 hemisphere (see also section 3. 0). The design shall allow 

 convenient access to the preamplifier and calibrate resis- 

 tor using only simple tools such as a screwdriver and 

 small wrench. Remolding or revulcanizing is unacceptable. 



2. 5 Cable and Connector. 



The assembly shall be supplied with 18 inches of water- 

 proof low-noise cable and connector attached. 



2.5.1 Cable. Five conductors (six conductors accept- 

 able), cable strength sufficiently adequate to support the 

 hydrophone assembly. 



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