Search devices for locating buried persons based on transmitter and reception deices using a frequency of 457 kHz, especially for the search of persons buried by avalanches, have been in use for a longer period of time (compare patent DE 35 31 726 C1).
These devices suffer from a substantial disadvantage that is caused by the propagation of the electromagnetic field of their ferrite antenna (compare patent DE 193 10 875 C1) and the fact that the latter signal is only received by one antenna, i.e., only parallel orientation of the antennae leads to the detection of maximum signal strength given the closest distance to the transmitter. If a perpendicular orientation of the two antennae is given, several maximum signal strengths may occur, which are not in the closest distance to the transmitter. Concerning the search for buried persons the problem arises that the latter fact is taken into consideration by the application of time-consuming and highly complicated methods, which also require a substantial amount of training (compare xe2x80x9cDe Alpenxe2x80x9d 11/1996xe2x80x94Mitteilungen des Schweizer Alpenclubs).
The invention disclosed in the patent DE 195 10 875 C1 also turns out to be less practical, because at first, there are three transmitter antennae located perpendicular to each other, which would render such a device very voluminous and make it impossible to wear it on the body, and second, a proper operation could only be ensured, if transmitter and receiver are of the same type, which excludes an integration into the already existing wide-spread types of devices. More recent devices, which make use of two perpendicular antennae (compare patent EP 0 855 600 A2), merely improve the first phase of the search for buried persons. An accurate localization to the point, however, cannot be achieved.
The invention is aimed at designing a search device for locating buried persons in a manner that allows the searcher to be guided easily and directly to the buried person, the latter being also possible with the above-mentioned wide-spread types of devices.
USPTO Backgrounds
USPTO Backgrounds