Abstract The majority of PCM recorders are used for recording quasistatic parameters such as temperature and pressure. The data rate of these recorders is usually up to 2 kbit/s. Even if a faster playback is used, the data rate will be less than 20 kbit/s. A microprocessor-based decommutator with a small amount of hardware to convert the serial data into parallel data would be able to handle this data rate comfortably. Such a decommutator would also be very cost effective in the above application. This paper describes a decommutator built around a microprocessor and its applications for ground processing and in situ calibration.