A received circuit receives a plurality signals generated by modulating carrier waves having the substantial same frequency according to digital signals having different bitrates output from a plurality of systems. The housing has a cylindrical wall. At least some of the chain links have at least one cross-member connecting the opposing straps. The optical system is adapted to provide an image of the first elements when light reflects off a surface of a test object, passes through the aperture, and is received by the detector array. The cutting blade inserts may comprise a composite material having a continuous metal matrix with hard metal carbide particles dispersed therein. Most preferably, the BCF yarns are formed of nylon-6 and exhibit an alpha-crystalline content of less than about 45%, and usually between about 45% to about 55%.