Abstract: A method of adding time information to a data stream is provided. First and second timing sequences are linked with the data stream. The first timing sequence provides a permanent time record of when the data in the stream first originated. The second timing sequence is re-writable when the data stream is altered, for example by editing, so as to ensure an internally consistent time track is provided each time the data stream is changed. The timing sequences are derived from absolute references such as Global Positioning System (GPS) Time. The first and second timing sequences may be stored separately to the data stream. Two or more sets of second timing sequences may be provided, corresponding to different presentations of common sets of data streams.

Abstract: A system for locating any mobile body of a plurality thereof within a predetermined environment, wherein each mobile body carries a transmitter (10 to 18), each transmitter producing a unique identifying signal, and a plurality of receivers (20 to 32) located in a corresponding plurality of defined regions in the environment, each receiver incorporating a FIFO buffer memory (28) into which carrier identifying data is inserted and a controller for interrogating the receiver means in turn to link the identification data with location data. (FIG. 1 ). A carrier authentication system is also described.

Abstract: A system for locating any mobile body or a plurality thereof within a predetermined environment, wherein each mobile body carries a transmitter (10 to 18), each transmitter producing a unique identifying signal, and a plurality of receivers (20 to 32) located in a corresponding plurality of defined regions in the environment, each receiver incorporating a FIFO buffer memory (28) into which carrier identifying data is inserted and a controller for interrogating the receiver means in turn to link the identification data with location data.