A stimulation system (301) for monitoring an elevator system, including a main controller (302) having a trigger output (312) for sending trigger signals and configurable to receive detection signals from sensors of the elevator system, and an activation controller (304) connectable to a input unit of an elevator car and having a trigger input (316) for receiving trigger signals that is connected to the trigger output; the activation controller is configured to, when connected to the input unit, cause activation, in response to a trigger signal (406), of predetermined operational signals at the input unit; and the main controller is configured to, when configured to receive the detection signals from the sensors, send (404) the trigger signal, and determine based on detection signals whether at least one change of the operating state occurs in accordance with the at least one predetermined operational signal.