An imaging system has a transmission system for transmitting a modulated optical signal and a reception system for receiving a received optical signal which is a reflected and delayed version of the transmitted signal. In the invention, a temporary user subscription is created for the roaming subscriber and an account balance is set for the temporary user subscription allowing the subscriber to use services attached to the temporary user subscription while roaming in the packet data based mobile communication network. The nozzle also includes a central tongue-holding part which has resilient hook-shaped engagement elements at opposite ends. Electronic device assemblies and systems include such substrates.