Abstract: An ambulatory heart monitoring apparatus (1) is provided with a slot (3) for receiving an IC card (2). A user places electrodes (7,8) on his body. Operation of a switch (5) causes the apparatus to record EGG signals from the electrodes (7,8) onto the IC card (2). Operation data, including, for example, battery voltage data, data representing the impedance between the electrodes (7,8) and calibration data, are stored on the IC card (2) in association with the recorded ECG signal. The operation data is useful for managing remote subjects. Also the calibration data can be used to normalize the recorded ECG data when it is processed at a remote processing station.