| 摘要 |
<p>The present industrial invention refers to a system and device used to automatically determine the position of an entity with respect to two or more reference entities; the said system is based on the transmission of two consecutive coded signals, with pre-determined time interval, by a reference source. The first signal is sent by means of radio waves and the second signal by means of acoustic waves; the second signal is followed by an acoustic signal emitted by another reference entity after a present time interval.</p> |
