Commission devices (1) comprise first transmitters (11) for transmitting activation signals to load devices (2-6), and second transmitters (12) for transmitting numbers of challenge signals to activated load devices (2) that respond by sending back a response signal per challenge signal to the commission devices (1). The commission devices (1) further comprise first receivers (13) for receiving the response signals and controllers (14) for determining time-intervals present between transmissions of the challenge signals and receptions of the response signals. The controllers (14) derive absolute or relative positions of the load devices (2-6) from analyzes such as statistical analyzes of the time-intervals. Load devices (2-6) comprise second receivers (21) for receiving the activation signals and third receivers (22) for receiving the number of challenge signals and third transmitters (23) for sending back the response signals to the commission devices (1). The load devices (2-6) may further comprise loads (26).