A service providing system includes a mobile apparatus that moves to a user in response to receiving an instruction to provide a service from the user and provides the service to the user after obtaining approval; and a client apparatus that manages a schedule input by the user, and, in response to receiving the instruction, transmits an instruction which is derived from the received instruction, the received instruction including information of at least one of a designated date and time and a designated location at which the service is to be provided. The client apparatus includes a display that displays a schedule in which a service providing schedule is added to the schedule input by the user according to a schedule display instruction, and the mobile apparatus moves to a scheduled location at a scheduled date and time and provides the service.

The present invention provides a method and an associated time manager for managing a time relation between system times of different remote systems, including: at a first moment, obtaining a first value of a first system time and accessing a periodically updating reference counter to obtain a first count; at a second moment, updating the time relation by: obtaining a second value of a second system time along with a second count, and calculating a second value of the first system time by summing the first value of the first system time and an extrapolation interval calculated according to a difference between the first count and the second count. Thus, when synchronization with a first remote system ends, a fourth value of the first system time may be calculated according to a fourth value of the second system time and a previously stored time relation.

A phase comparison circuit for outputting a phase difference signal indicating a phase difference between a data signal and a clock signal is disclosed. The disclosed phase comparison circuit includes: a detection part for outputting a plurality of signals indicating phases of the data signal according to different decision threshold levels; a phase comparison part for outputting phase difference signals each indicating a phase difference between a signal in the plurality of signals output from the detection part and the clock signal; and a control part for determining whether to output a particular phase difference signal in the phase difference signals by using the whole or a part of the phase deference signals.

The invention discloses a constellation of relay vehicles comprising a receiver of navigation signals and a transmitter of positioning signals to an area of service where a number of rovers manoeuver, wherein the position of the relay vehicle may be adjusted to optimize one or more of an SNR or a DOP index of the positioning signals. In some embodiments, the optimal configuration of the constellation of relay vehicles may be further defined based on priority indexes allocated to the rovers. The invention is applicable to terrestrial or underwater rovers, respectively serviced by aerial or nautical relay vehicles.

A site management system may include a user interface with a display device, a network interface, and a controller coupled to the user interface and the network interface. In some examples, the controller may be configured to determine the location of a first machine and compare the location of the first machine to one or more second machines. After determining the first machine crosses a predetermined geo-boundary of a second machine, the controller may be configured to elevate a threat level associated with the second machine.