Connection establishment in elevator system, escalator system or autowalk system

The present invention relates to a method for initiating a data connection between a central server (300) and a control unit (120) communicatively coupled to an elevator (100), escalator or autowalk. The method comprises: receiving a trigger signal (410) from the central server (300), wherein the trigger signal is delivered with a service of a mobile communication network into which the control unit (120) is communicatively coupled to; detecting (420) if the trigger signal complies with at least one pre-defined requirement; and in response to a positive outcome of the detection initiating a data connection establishment (430) from the control unit (120) to the central server (300). The invention also relates to a control unit for an elevator, escalator or autowalk.