A small battery-driven transponder was developed from an Edgerton pinger, a hydrophone, and an amplifier. The transponder was used in the Charles River. It was demonstrated that distances from the transponder could be determined to within 2.7 feet. The maximum distance recorded was 1200 feet. As further application of the transponder, it was decided to attempt to run a search pattern of a series of concentric circles with the transponder at the center. Due to difficulties in equipment other than the transponder, it proved difficult to cruise in such a circle. With the transducer looking at the bottom, the transponder ceased to run in sync at distances greater than 400 feet. (Author)
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