ballistic shock wave first intercepted the metallic sensor rod and travel in opposite directions toward the ends of the rod. Transducers located on the ends of the rod detect the shock waves in the metal rod and produce electrical signals which start and stop timing circuits. The relative time difference of the start and stop signals from the opposite ends of the rod sensor, coupled with the known velocity of sound in the metallic rod, allows calculation of the impact point on the linear rod. Each rod sensor, one vertical and one horizontal, acts independently of the other to produce one axis of the XY-coordinate grid which defines the target area. The intercept of the XY-coordinates defines the "hit" for a projectile which passes through that intercept point.The resulting "hit" data are displayed as digital numbers representing the distance from the target center or displayed in graphic form as a dot on a display screen.
Curved rod sensors as described in U.S. Pat. Nos. 5,025,424 and 4,351,026 function in a like manner to the linear rod sensors but define the XY-coordinates of a "hit" as the intersection of two radial lines, where each radial line passes through the center of curvature and the tangent score point of a curved rod sensor. At least two curved rod sensors are placed on the same side of the target area to produce radial lines which intersect in the target area and define the "hit" coordinates. Both curved rods are placed below the line of fire and away from possible