The present invention is concerned with an electronic module (2) for attachment to a drug delivery device. The electronic module includes delivery status sensing means (21,22) for monitoring a delivery status of the delivery device, a status indicator (25) with an indicator element such as a Light Emitting Diode controllable to indicate a delivery or module status, and a status indicator controller (23). The status indicator controller is configured to generate an indicator control signal on behalf of the status indicator element which in turn produces a status signal. The indicator control signal has an amplitude varying monotonically in time between a minimum value and a maximum value in a first interval of a base cycle, and between the maximum value and the minimum value in a second interval of the base cycle. In at least one of the first and the second interval, the mean value of the indicator control signal is below the average of the maximum and the minimum values of the indicator control signal. Increased energy savings are realized, which benefits the capacity requirements of a non-replaceable battery.
