A dual complementary target arrangement is provided which enables the targets to be formed as an integral part of a cam shaft. By machining first and second radially enlarged integral portions of a shaft, complementary targets are provided which each comprise segments of differing radial dimension measured from the central axis of the shaft. By permitting the formation of the rotatable targets as an integral portion of a cam shaft, the complementary targets can be incorporated as an integral portion of an automobile engine without necessitating the prefabrication of complementary targets and subsequent attachment of the targets to a cam shaft. Not only does the unitary structure of the cam shaft reduce the manufacturing costs of the target and shaft combination, but in certain applications it makes possible the use of complementary targets within the structure of an automobile engine where the use of individual components attached together would not be practical.