Abstract: A method whereby a moving body searches for an unoccupied time slot in a time-division communications channel for the transmission of a message. The moving body participates with other moving bodies located in the same geographical zone in an anti-collision system with the time being conventionally divided into reproducible time periods T. Each period includes a number N of time slots reference 1, 2, 3 . . . i . . N with the access to a time slot for the transmission of a message from the moving body being accomplished by identifying an unoccupied time slot during at least one listening period T, followed by a random choice of one slot i from among the slots identified as being unoccupied. For at least one period after the moving body has occupied slot i, the time of this slot is divided randomly into reception sub-slots R and transmission sub-slots E.

Abstract: A system for sea navigation which features a plurality of ships located in a single high density area (for example port) and a control center for this area using a common transmission channel. The ships are equipped to transmit data about their speed, heading and position, which are displayed on a panoramic screen fitted on all ships and in the control center. The control center has priority access to this common channel to send general interest messages or special messages to all or some of the equipped ships.

Abstract: A collision avoidance system for sea navigation comprises, for each equipped ship, a transmitter that repeatedly transmits the geographic coordinates, course and speed of its own ship and a receiver that sends a display device similar data received from other ships. These received data are displayed, mostly in the form of symbols, on the panoramic screen of the display device.

Abstract: The disclosed system has, for each equipped ship, a transmitter that repetitively transmits the geographical coordinates, speed and course of its own ship. Furthermore, it transmits an identification code of any nature serving as an address for the exchange of messages. If it wishes to make concerted arrangements with other surrounding ships in order to perform maneuvers, it sends encoded messages taken out of a glossary.