Digitally controlled phase interpolator circuit. The low frequency restoration circuit operates to extract low frequency information prior to being high-pass filtered by the AC coupling circuit. Highly efficacious drug candidates are identified by screening the libraries for binding and inhibitory activity against both HIV and FIV protease. The cam shaft is rotationally supported in the housing on a plurality of bearings, and the cam gear is rotationally supported on a stub shaft with an inner surface that is out of contact with the cam shaft. The memory then stores road speed data relating to different type of road on which the vehicle may travel, so that the processor means can compare also the sensed vehicle speed with the road speed data in order to help deduce the type of road on which the vehicle travels.