A light source includes a light head and a heat transfer arrangement. A hydraulic system includes an actuator, a hydraulic coupler that includes substantially incompressible hydraulic liquid, and a container. An interpolation data generator is provided which repeatedly puts out a predefined interpolation datum for insertion in each uncorrectable or uncorrected error location in the digital signal whenever such an error is detected by the error-detecting and -correcting circuit. as measured by ASTM D1238, condition L. , pain, itch, cough, asthma, or inflammatory bowel disease.