52 



The RS/904 can also operate with responder beacons. The only difference 

 between responders and transponders is that, in the case of responders, the 

 beacons are interrogated electrically, by cable. The RS/904 then determines 

 position by techniques similar to those used in transponder operation, instead 

 of measuring the signal's two-way propagation time: however, the hydrophone 

 only measures the one-way propagation time of the response signal. This 

 method, which yields greater accuracy than acoustics alone, is particularly 

 useful for applications involving remotely operated vehicles. In transponder 

 and responder operations, knowledge of depth is not required for position 

 calculations, although use of a depth- telemetry transponder can provide greater 

 accuracy. 



Operating frequencies for the RS/904 system include: interrogate - 3 channels 

 at 13, 15 and 17 kHz; response - nine channels in the 22 to 30 kHz band at 

 1 kHz intervals. The system is accurate within 1 percent of slant range for 

 horizontal offsets up to 200 percent of water depth. With a depth- telemetry 

 transponder it is accurate within 1 percent of slant range for horizontal 

 offsets up to 400 percent of water depth. 



AMF 301 System - This system is used by British Oxygen Corporation, Ltd. and 

 Sub Sea Surveys Ltd. Shipboard equipment consists of a power amplifier, a 

 receiver, a coder and a transducer which is suspended in the water. Sub-surface 

 equipment consists of a compatible transponder which is affixed to the vehicle. 



The operational procedure involves manual or automatic interrogation of the 

 vehicle-mounted transponder from the support craft. Slant range to the vehicle 

 is displayed digitally on the receiver and bearing is displayed in analog format 

 through a full 360 degrees. Bearing angle (relative to the surface craft) 

 accuracy is -5 degrees, timing error (slant range is computed on the basis of 

 elapsed signal time from ship-to-transponder-to-ship) accuracy is ^0.5 milli- 

 seconds . 



The shipboard system operates on 90 to 115 VAC, 50 to 60 Hz, 250 watts. 

 receiver frequency is 10 kHz (standard) , 3 to 15 kHz are optional. 



The 



Wesmar SS210S Tracking System - The Wesmar system is used by COMEX Services 

 and Sonarmarine Ltd. The system's shipboard components consist of a console 

 (with CRT display and control functions)/ a soundome (containing a transducer 

 which can scan from to 350 degrees and can tilt the acoustic beam from 4 

 degrees above the horizontal to 90 degrees below), and an electrical hoist 

 system for deploying the soundome in or out of the water. Sub-surface equipment 

 consists of a vehicle-mounted transponder (Wesmar model T210) . 



The Wesmar system can operate in an active or passive mode. In the active 

 mode the transducer emits a short burst of acoustical energy (160 kHz) which 

 strikes the vehicle and is reflected back to the transducer where it is amplified,| 

 processed and displayed on the CRT. In the passive mode a transponder is 

 mounted on the vehicle. The transducer then transmits a 25 kHz pulse which is 

 received by the transponder and commands it to send a return pulse at 160 kHz. 

 The return signal is displayed to give range, bearing and depth of the vehicle. 

 The transducer in the soundome is stabilized to compensate for surface vessel 

 pitch and roll up to 25 degrees. 



