A set of rules and a current context for a user is obtained. A recess is formed in a substrate on which one or more integrated optical waveguides are disposed, the recess being located at the desired mounting location of the photonic integrated circuit. Each node reacts to a loss of light from another node in the same way: by rerouting incoming traffic from external sources from a working input-output interface to a protection interface, to establish a path for the protection signal, and by sending a signal enabling the two nodes to resume communication. A display is operably connected to the control unit for visually displaying a progression of the pit stop function in response to manipulation of the other control mechanism. The time-division duplex mobile communication system can achieve miniaturization, low power consumption and low costs by using a frequency conversion circuit including a mixer and an intermediate frequency circuit for both transmitter and receiver, and also can cope with multi-band, multi-application systems by using a broadband amplifier, a variable IF filter and a variable gain amplifier. The database may include descriptive information for respective logical volumes, such as users authorized to access the logical volume or the user which created the logical volume.