a portable device for communication is useable during movement by a person . individual portable receivers , the size of a credit card , display and / or broadcast to a user , automatically or by selection , data coming via waves coming from microwave or laser transmitters and fm transmitters . the transmitters can cover nerve zones such as population centers , and sequentially send a flow of data transmitted by a digital signal with for instance 900 , 000 bits / second . at the same time , the transmitters are used to cover 95 % of a territory in audio . this provides a service of public interest , allows changing the descriptive speech , provides a choice of messages , offers a presale service , and makes possible selective identification . the device also automatically pinpoints a position with a single transmitter and provides a target objective that is sought to be reached by the user , thus simultaneously meeting the requirements of urban , rural and interior location while being useable with all locomotion means .