Abstract: A racquet is provided having a transverse compliant edge system that supports the racquet strings and has independent elastic transverse movement of the string supports while inhibiting accompanying radial movement. The transverse compliant edge system includes rigid string support rails inside an outer channel in the racquet frame. Each string support rail has an outer groove that contains and supports the racquet string and an inside contact surface supported by the racquet frame and that acts as a pivot point. The string support rails are spaced away from the walls of the outer channel in the racquet frame and the spaces are bridged with compliant material or springs. This arrangement allows the string support rail to rotate about its inside contact surface pivot, thus allowing elastic transverse string movement while inhibiting accompanying radial movement, independent of transverse string movement caused by the elasticity of the ball, strings, or racquet.

Abstract: An underwater transducer having both projector and hydrophone elements utilizes a new technique permitting the annular projector rings of a given piezoelectric material and resonant frequency to be tailored in diameter to accommodate various requirements, such as a need for more interior space. Where the projector rings can be expanded to the diameter of an accompanying hydrophone array, this makes possible a more compact and, in particular, a shorter structure than has been used for transducers of similar capability before. In the transducer the projector rings are positioned axially along a central support tube alternating with the hydrophones arranged in annular groups. Each projector ring is formed of a plurality of segments of alternately active material and inactive material having a sound velocity differing from (usually faster than) that of the active material.