Portion of a test or procedure (containing both a technical and a professional component) that pertains to the use of the equipment, supplies, materials, and the operator (technician) that performs it but does not interpret the results (i.e., electrocardiograph [ECG] machine and technician, radiography machine and technician, microscope and technician). When billing using CPT codes, a service that is TC only should not be billed with a two-digit modifier. See also professional component (PC) .