The transducers should be calibrated every year. This can be done either by your local calibration service or by the Swap Calibration Service, which we offer on request. The Swap calibration service reduces downtime to a minimum as the freshly calibrated replacement transducer is shipped and can simply be plugged into the audiometer to start working. The uncalibrated transducer is returned in the same shipping carton. A return label is included in the box.