EP1785168A1 - Search device - Google Patents

Abstract

The person walking or skiing in an area where an avalanche can be expected is equipped with a portable detection device. The device is fitted with speed sensors reacting on movements performed in three different directions. The sensors are capable of differentiating between a quick motion, meaning the user is not covered by snow and still skiing or walking, a slowed down motion meaning the user is covered but still alive, or no motion at all meaning the person has died. The information about a movement like a heart beat or the breathing is transmitted to the rescue station. Independent claims are given for a method using the device, another, slightly different device, a method for using that device, an aerial for a short range communication system, and a device incorporating the aerial.

Description

Technical area

The invention relates to a search device, in particular an avalanche victim search device (LVS), a method for determining a movement state of such a search device, a method for transmitting a transmission signal with such a search device and an antenna unit for a short-range radio system.

State of the art

In European Telecom Standard ETS 300718, Radio Equipment and Systems (RES); Avalanche beacons; Transmitter-receiver systems, ETSI March 1997 all important standards and regulations for such avalanche beacons are defined and described.

The state of the art should be exemplified at this point EP 1 577 679 A1 mentioned, in which a search device for locating a transmitter, in particular an avalanche victim search device is described.

The invention relates in particular to search devices which comprise a transmitting / receiving device with which a transmission signal can be transmitted in normal operation (transmission). Due to this transmission signal, the device or the user who carries the device with him, be located in case that the user and his device is buried by an avalanche. A rescuer who also carries such a device can switch his device to "search mode" (search mode) in the event of an avalanche, so that the transmitted signal from the victim's device can be received and the victim's device can be located on the basis of this signal.

Presentation of the invention glossary

AT THE

amplitude modulation

LVS

Avalanche victims Suchgerätz

SRD

Short Range Devices (according to standard ETS 300220), radio transceivers with short range, which may be operated license-free

1 Recognition of life signs of the victims 1.1 Motivation

Experiences with avalanche accidents show: The chances of success, that buried people can be recovered alive and without permanent health damages, are high, if the salvage within z. B. 15 min after the avalanche decline can take place. The efficiency of the rescue could be significantly increased if the rescuers aware of the current medical condition of the rescuing Have buried. The salvage could first be concentrated on those victims who survived the actual avalanche decline.

• ■ Verschüttungsdauer?
• ■ Hat (hatte) der Verschüttete noch erkennbare Lebenszeichen?
• ■ Seit wann hatte der Verschüttete keine erkennbaren Lebenszeichen mehr?

Keines der aus dem Stand der Technik bekannten LVS umfasst irgendwelche Mittel zum Feststellen des Vitalzustands des Benutzers, der das LVS bei sich trägt, insbesondere für den Fall, dass der Benutzer von einer Lawine verschüttet ist.In addition, the efficiency of medical treatment of avalanche victims after salvage (triage, resuscitation, transport to hospital, etc.) can be significantly increased if important information is available. In this context, answers to, for example, the following questions would be valuable:

• ■ Spill duration?
• ■ Has the victim still had recognizable signs of life?
• ■ Since when did the victim no longer have any recognizable signs of life?

None of the avalanche transceivers known in the art includes any means for determining the vital state of the user carrying the avalanche transceiver, particularly in the event that the user is buried by an avalanche.

1.2 Idea overview

1. 1. The LVS are provided with a device that can detect the medical condition of the victim with, for the considered application, sufficient informative value and sufficient reliability. Already very helpful would be the statement: "The buried still has signs of life".
2. 2. The WMS displays important medical treatment data on the victim's WMS screen. This information can be retrieved at any time after the recovery, on the transport to the hospital or in the hospital.
3. 3. If a buried person still has a vital sign and is "targeted" by the search device of a rescuer when searching for buried subjects, the vital condition of the victim is displayed on the rescuer's transceiver. For this purpose, for example, a wireless transmission of this data from the avalanche transceiver to the avalanche transceiver of the rescuer is necessary (see Chapter 3).

1.3 Realization 1.3.1 Description of the device

1. 1. The detection of signs of life is realized with an acceleration sensor (sensor means).
2. 2. To ensure a reliable, position-independent function, a 3-axis accelerometer (x, y, z axis) is used.
3. 3. The acceleration sensor is fixed in the avalanche transceiver.
4. 4. A suitable, currently available acceleration sensor is the LIS3L02 from ST Semiconductors.
5. 5. This accelerometer can be fitted on an electronic circuit board of the transceiver.
6. 6. When the user uses the WMS, for example, he wears it on his body in a special carrying device or in a trouser pocket. The acceleration sensor can now monitor the vital state of the user, i. H. certain "vital signs" of the user due to the movements of the user taking part in the WMS.
7. 7. If the user is buried by an avalanche, z. B. typical movements of the following type: heart pulse, pulse in a blood vessel, breathing, muscle movements (muscle twitching).
8. 8. The detected signals of the acceleration sensor (temporally resolved output signal) are processed and evaluated with a microcontroller or with a digital signal processor.
   
9. 9. Wiring of the acceleration sensor:
   
   The signals SPI_MOSl, SPI_MISO, SPl_CLK and SPI_ACC_SEL are connected directly to the (standardized) SPI interface of a microcontroller.
10. 10. The method for processing and evaluating the signals of the acceleration sensor (realized as software, for example) is described below (see 1.3.2).

1.3.2 Description of the detection method

1. 1. The acceleration sensor measures the acceleration on all three axes (x, y, z) at a fixed, suitable sampling rate.
2. 2. The samples of the three axes (x, y, z) are combined into one sample by adding them together.
3. 3. With a digital high-pass filter, the DC value is then eliminated.
4. 4. The absolute value is formed from the DC-free signal by reversing the sign in the case of negative values. This processing step can be understood as demodulation of an AM signal.
5. 5. The running average is formed from the absolute value signal with a digital low-pass filter.
6. 6. This resulting average is periodically compared to a threshold.
   1. a. If the mean value is greater than the threshold value (vital threshold value), this can be interpreted as a reliable sign of life. The "Status of vital signs" of the respective LVS user is set to "Sign of life present".
   2. b. If the mean value is less than the threshold value, the status is set to "unknown".
   Possible extension:
7. 7. In the case of the absolute value signal obtained in processing step 4, the frequency range of interest (for example 0.1 Hz ... 3 Hz) is highlighted with a bandpass filter.
8. 8. With this signal, a frequency analysis is performed by means of Fast Fourier Transformation (FFT).
9. 9. From the resulting amplitude spectrum, the maximum amplitude is searched.
10. 10. The frequency at which the maximum amplitude occurs is the cardiac pulse rate.
11. 11. A plausibility check is carried out
    1. a. whether the heart pulse rate has a plausible value
    2. b. whether the amplitude has a plausible value
    3. c. whether the status determined in points 7 and 8 = "sign of life exists".
12. 12. If true, the detected heart rate is declared valid and can be reported externally.
13. 13. If the plausibility check is not fulfilled, the heart rate is declared as "unknown".
    

1.4 feasibility

The described device and method have been implemented and tested with a prototype device. The results obtained confirm the feasibility.

Example of a test performed:

The above illustration shows the result of the frequency analysis (amplitude spectrum). The associated acceleration signal was recorded on a subject who lying on the ground, moving as little as possible and having put a prototype avalanche transceiver with accelerometer on the right thigh.

Result:

In the resulting amplitude spectrum, the heart rate is approximately 1.6 Hz (= 96 beats per minute) clearly visible.

2 Determination and evaluation of the current avalanche transient state 2.1 Motivation

In the case of known avalanche transceivers, the (switched on) device is either in normal operation (transmission mode) or in search mode, if this has been set accordingly by the user. If an avalanche transceiver (= "normal operation") could reliably determine that it is not currently covered by an avalanche, it could use this information to make significant system optimizations.

2.2 Idea overview

1. 1. The transceivers are provided with a device that can reliably detect that it has not been spilled by an avalanche.
2. 2. In combination with the life sign recognition (see chapter 1), the following states can be distinguished:
   1. a. "A lot of movement". The avalanche transceiver is not spilled by an avalanche
   2. b. "Little movement, signs of life detected". The avalanche transceiver could be spilled by an avalanche. The user has unique signs of life.
   3. c. "No movement, no signs of life". The avalanche transceiver could be spilled by an avalanche. The user has no more life signs.
   4. d. "Unknown condition". It is not possible to assign a unique state. This is z. B. immediately after switching on the device of the case.
3. 3. Depending on the state of motion of the WMS, further measures can be taken. For example, the LVS in the "high movement" state (see above, a) can take the following measures, which are permissible only if the avalanche transceiver is not spilled:
   1. a. The transmission power of the 457 kHz LVS signal is reduced, for. B. on the gem. LVS standard ETS 300718 permissible minimum. A reduction by a factor of 10 can be realized. This reduces the power consumption of the transceiver in the "transmit" mode. The battery life can be increased accordingly with this measure.
   2. b. The pulse duration of the 457 kHz LVS signal (transmit signal) is reduced, eg. B. on the gem. LVS standard ETS 300718 permissible minimum. This further reduces the power consumption of the transceiver in transmit mode and increases battery life accordingly.
   3. c. The transmission pulses can z. B. within the existing in a ski tour group WMS 'time coordinated, ie the temporal position of the transmission pulses can be varied or moved. This measure is dealt with separately in Chapter 5.
   This means that these measures will not be taken if the avalanche transceiver is not in the "high movement" state.
4. 4. In case of after avalanche, d. H. If rescuers are spilled by another avalanche, the concerned avalanche transceivers can recognize this "change of state" of the rescuer or his avalanche transceiver and immediately place the avalanche transceiver in the "send" operating state. Thus, the respective WMS can be located by the WMS of non-buried rescuers.

2.3 Realization 2.3.1 Description of the device

1. 1. The differentiation of the different states is realized with the acceleration sensor as described in chapter 1.3.1.
2. 2. An additional electronic compass can be used as second sensor (see chapter 6). However, this is only suitable for detecting the condition "a lot of movement".

2.3.2 Description of the procedure

1. 1. The basic signal processing is performed according to the procedure described in chapter 1.3.2, points 1 to 7.
2. 2. The result evaluation of chapter 1.3.2, point 8, now takes place again with 2 threshold values.
   The resulting average is periodically compared with these thresholds, based on this comparison, the current state is determined.
   1. a. If the running mean value is greater than the upper threshold (movement threshold): current state = "a lot of movement"
   2. b. If the mean value lies between the lower threshold value (vital threshold value) and the upper threshold value (movement threshold value): current status = "little movement, signs of life present"
   3. c. If the mean value is smaller than the lower threshold value (vital threshold value): current status = "no movement, no vital signs"
      

2.4 Feasibility

• durchgezogene Linie: Absolutwertsignal
• gepunktete Linie: laufender Mittelwert (Grundlage für Ermittlung des LVS-Status)

The described device and method have been implemented and tested with a prototype device. The results confirmed the feasibility. Example of a test performed:

• solid line: absolute value signal
• dotted line: running average (basis for determining the LVS status)

0s ... 42s:

Die Testperson läuft mit dem Prototyp-LVS herum.

42s ... 92s:

Die Testperson liegt auf dem Boden; das Prototyp-LVS ist auf den rechten Oberschenkel gelegt.

92s ... 130s:

Das LVS wird den Boden gelegt und nicht bewegt.

Three different states were recorded:

0s ... 42s:

The subject walks around with the prototype avalanche transceiver.

42s ... 92s:

The subject lies on the ground; the prototype avalanche transceiver is placed on the right thigh.

92s ... 130s:

The avalanche is placed on the ground and not moved.

The acceleration sensor signals were recorded separately for each state. Thereafter, these were assembled into a state sequence and passed as an input to a simulation of the described method.

The most important result is:

The level of the "determining average value of the absolute value signal" which determines the state determination differs in each case by about 20 dB in the three states of interest. This can be a clear and reliable distinction of the defined states are performed.

3 wireless data channel 3.1 Motivation

Known avalanche beacons have the ability to send and receive the locator pulses. However, the transmission of any information between two such search devices using these locating pulses is only possible to a limited extent. There is no known search device that allows efficient communication between such search devices.

With the possibility of wireless communication among the avalanche transceivers, further substantial optimizations and comfort increases of the avalanche transceiver system are possible.

3.2 Idea Overview

1. 1. The WMSs are provided with a wireless communication device which enables communication among several WMSs.
2. 2. Wireless communication is via radio.
3. 3. Frequency bands are used, which are released for the license-free operation of so-called Short Ranges Devices (SRD).
4. 4. In addition, these frequency bands must be well suited to the propagation conditions in the snow, ie in snowy terrain and through the existing snow cover. According to a study, frequencies below one GHz are particularly suitable for this purpose. The suitable SRD frequency bands are for example 433 MHz, 868 MHz and 902 ... 928 MHz. The expected range is in the range 20 m .. 100 m.
5. 5. The range of a single transceiver can be increased with the repeater function: The transceivers forward received messages to other transceivers.
6. 6. In the "Send" state, the transceivers transmit an identification message via the radio channel in temporal coordination with the 457 kHz-LVS transmit pulses. These radio messages are used as another feature for the search of victims. Because the radio identification messages are much shorter than the LVS pulses (2ms instead of 70ms ... 300ms), the problem of temporal overlap can be greatly mitigated.
7. 7. The current state of the victim can be transmitted to the search device and displayed there in a suitable manner (see Chapters 1 and 2).
8. 8. The coordination of the temporal position of the 457 kHz LVS transmission pulses can be carried out by means of communication via the radio channel (see also chapter 5.3.1.2).
9. 9. The spill search can be optimized by coordinating the search devices over the radio channel:
   1. a. The search devices coordinate so that not several rescuers simultaneously seek the same buried. To distinguish the various buried avalanche transceivers, the identification messages described in point 6 are evaluated. If a rescuer "targets" a victim who has already been "targeted" by another rescuer, this will be displayed as a warning on the display of his avalanche transceiver.
   2. b. In order to provide the search algorithm with additional information, the LVS, which are set to search, respectively exchange the determined situation data via the radio channel with each other. Such situation data are z. B. List of detected transmitting WMS ("WMS database") with associated identification, distance, direction and with the determined 457 kHz signal parameters (period and temporal position).
10. 10. Spill search can be optimized by reducing the level of the 457kHz LVS signal from spilled LVS found. The necessary communication takes place via the radio channel. This situation can be mitigated with multiple burials because the likelihood of overlapping 457 kHz pulses is reduced. For safety reasons, this level reduction takes place only temporarily during z. B. 10 min.
11. 11. If, after an avalanche, a non-buried person forgets to set their beacon to "seek," this beacon interferes with its 457 kHz transmit beacon signal. This situation can be defused. As soon as an avalanche transceiver is set to search, this communicates the current state via radio channel to the other avalanche beacons. An avalanche transceiver that is in the "high movement" state (see chapter 2) in this situation, ie does not spill, alerts its user with an audible warning signal and a corresponding warning message on the avalanche transceiver display.
12. 12. The radio channel is used as a service interface for the following purposes:
    1. a. Parameterization: New parameters can be read by a data processing device, eg. B. from a PC, are transmitted to the LVS '.
    2. b. Software updates: New software versions can, for example, be transferred from a PC to the LVS '.
    3. c. Service tests: A test facility can communicate with the LVS to be tested via the radio channel and in this way transmit test and calibration commands.

3.3 Realization 3.3.1 Description of the device

1. 1. Die LVS werden mit einem SRD-Transceiver ausgerüstet.
2. 2. Es wird ein Single-Chip Transceiver (z. B. nRF905 von nordic Semiconductor) eingesetzt.
3. 3. Es wird eine Antenne eingesetzt, die eines oder mehrere der entsprechenden Frequenzbänder abdecken kann (siehe Kapitel 4).
4. 4. Beschaltung des SRD-Transceivers:
   • Die Schnittstellensignale (längliche Rechtecke mit Pfeil-artigen Enden) werden alle auf einen Microcontroller geführt.

1. 1. The transceivers are equipped with an SRD transceiver.
2. 2. A single-chip transceiver (eg nRF905 from nordic Semiconductor) is used.
3. 3. An antenna is used which can cover one or more of the corresponding frequency bands (see chapter 4).
4. 4. Wiring of the SRD transceiver:
   • The interface signals (elongated rectangles with arrow-like ends) are all routed to a microcontroller.

3.4 feasibility

The above circuit was implemented in prototype devices and put into operation.

Radio testing with 868 MHz test transmitters buried 2 m below the snow cover confirms that a sufficient range can be achieved even under these conditions.

4 multiband antenna 4.1 Motivation

For example, in GSM mobile phones, it is known to use antennas that have multiple resonances. On the other hand, no antennas for SRD devices are known which could be used for two or more frequency ranges. In addition, the rod antennas for mobile phones based on other ideas than those for such SRD devices.

Short Range Devices (SRD) are short-range radio systems that can be operated license-free. The approved frequency bands suitable for the operation of the LVS data channel acc. Chapter 3 are 868 MHz in Europe and 902 MHz ... 915 MHz in the USA / Canada. With an antenna that can be used for both frequency ranges, there is no need to distinguish between device variants for the European and American markets become. Thus, the additional costs for production and logistics can be avoided. Such an antenna could also be used for other SRD applications apart from the radio application in the LVS.

4.2 Idea overview

1. 1. An antenna (antenna unit) is used which emits as much power as possible at the two desired frequencies (868 MHz and approx. 915 MHz). This can be achieved with an antenna which has a resonance point on both frequencies.
2. 2. The two resonant locations can be achieved when the antenna and associated matching circuitry form a supercritically coupled dual-band bandpass filter.

In principle, it would also be possible to realize an antenna which has a resonance point for more than two frequencies and would therefore be usable for more than two frequency ranges.

4.3 Realization 4.3.1 Description of the device

1. 1. The antenna with wiring is shown in the following sketch:
   
2. 2. A loop antenna is used as antenna (E301).
3. 3. It is executed as a stamped part, which is fitted on the LVS circuit board.
4. 4. Together with C322, C312 and C306, it forms the first loop of the bandpass filter.
5. 5. The inductor L303 together with the capacitors C305, C321, C311, C308, C309 and C310 form the second loop of the bandpass filter.
6. 6. The inductance L303 is designed as a wire loop. It is populated on the LVS circuit board. With this form of realization can be achieved a sufficiently high quality.
7. 7. The two circuits are connected via C306. It is also influenced by C308, C309 and C310.
8. 8. The received signal is coupled out via C305 or the transmission signal is coupled in. At this point, an impedance of about 50 ohms is measured at the desired frequencies.
9. 9. The antenna is tuned by the choice of capacitance values as well as the geometrical dimensions of the antenna and the inductance. The following influences must be included:
   1. a. Execution of the printed circuit board. Material (Dielectric), Thickness
   2. b. Placement of the antenna and the remaining components on the PCB
   3. c. Environment of the antenna. Other components in the WMS, such as As display, battery, etc.
   4. d. Material of the housing plastic (damping, dielectricity)

4.3.2 Feasibility

From the antenna described a prototype was built and measured.

A network analyzer was used to record the input reflection factor S ₁₁ at the coupling point in the range 700 MHz to 1.2 GHz (see below). The two markers are set to the two desired frequencies 868 MHz and 915 MHz.

The measurement shows that both markers are almost exactly in the center, so the reflection factor is practically zero at both frequencies. This means that the antenna including the circuitry is optimally tuned at both frequencies.

5 Coordination of the LVS transmission pulses 5.1 Motivation

In the known search devices, a search device transmits its locating pulses without taking into account the locating pulses of other devices, so that the transmission pulses of the 457 kHz transceiver signal from several transceivers can temporally overlap. The search of several persons with avalanche transceivers that are spilled is therefore a difficult task according to the current state of the art. In most cases, it will only succeed with targeted strategies by trained rescuers. If the pulses of several avalanche transceivers overlap, they can hardly or no longer be distinguished from the other search devices.

If it is possible to time-coordinate the 457 kHz transmit pulses of several WMSs so that they do not overlap (or at least less), this can considerably facilitate the search for several buried victims.

5.2 Idea overview

1. 1. The transceivers are equipped with one or more methods which coordinate the pulses of the 457kHz LVS transmit signal.
2. 2. This coordination of transmission pulses may no longer take place if there is a spill as a result of an avalanche decline. For this purpose, this method is coupled with the idea described in Chapter 2 "Determination and evaluation of the current LVS movement state". Coordination will only be done when the lvs is in the high movement state, so it can not be spilled by an avalanche.
3. 3. A method based solely on the 457 kHz system can be used. This procedure can take into account the signals from all the WMSs that comply with the WMS standard ETS 300718.
4. 4. A method that performs the coordination over the wireless communication channel may be used. This procedure may be more efficient than that listed under point 3. Disadvantage: WMS without wireless communication channel can not be considered.
5. 5. A combination of the two aforementioned methods can be used, so that the advantages are retained and the disadvantages can be excluded.

The search device has corresponding coordination means for coordinating a time position of the transmission pulses of the own transmission signal with a temporal position of the transmission pulses of the other search device.

5.3 Realization 5.3.1 Description of the procedures 5.3.1.1 Based only on 457 kHz signal

1. 1. The following procedure is only activated if the transceiver is in the "high movement" state (see chapter 2), ie not spilled by an avalanche.
2. 2. "Now and then" a transmission pulse is not sent. Instead, the 457 kHz receiver is activated in this time slot and it is checked whether an overlap takes place.
3. 3. Whether the transmission pulse acc. Point 2 is not to be sent, each with a random number generator with a hit rate of z. For example, 1/20.
4. 4. If the recipient acc. Point 2 in the time slot of interest does not receive an LVS transmitter, the current time position and the period of the transmission pulses is maintained.
5. 5. If the recipient acc. Point 2 in the time slot of interest detects at least one other LVS transmitter, the next transmit pulse is omitted and the test is repeated.
6. 6. If the recipient acc. Point 5 in the time slot of interest does not receive an LVS transmitter, the current time position and the period of the transmission pulses is maintained.
7. 7. If the recipient acc. Point 5 in the time slot of interest still recognizes at least one other transceiver, the time sending position is postponed (see point 8).
8. 8. The LVS shifts the position of the transmit pulse by a randomly selected integer multiple of the transmit pulse duration in a value range 1 .. 10. The pulse period is retained.
9. 9. The procedure repeats starting with point 1.

5.3.1.2 Based only on radio channel communication

1. 1. The following procedure is only activated if the transceiver is in the "high movement" state (see chapter 2), ie not spilled by an avalanche.
2. 2. The WMS maintains a WMS database listing all other WMSs received over the radio channel. Among other things, the identification and the timing are registered relative to their own system time.
3. 3. Based on this timing information, the WMS determines whether there is a temporal overlap of the 457 kHz transmission pulses with other WMSs, which can also communicate over the radio channel.
4. 4. If no free time slot is available, the least busy time slot is selected. If several time slots are occupied, a random time slot is selected.
5. 5. The new timeslot position will be announced to the other WMS via the radio channel.
6. 6. The procedure repeats starting with point 1.

5.3.1.3 Combination of the above methods

1. 1. The following procedure is only activated if the transceiver is in the "high movement" state (see chapter 2), ie not spilled by an avalanche.
2. 2. The WMS conducts the transmission pulse coordination acc. 5.3.1.2 by. This allows the LVS ', which are equipped with radio communication, to be coordinated.
3. 3. Additionally the avalanche transceiver checks acc. 5.3.1.1, if its 457 kHz transmission signal still overlaps with another one.
4. 4. If there is still an overlap, it randomly selects a new time slot, the gem. LVS database is free.
5. 5. The new timeslot position will be announced to the other WMS via the radio channel.
6. 6. The procedure repeats starting with point 1.

6 Interpolation of the LVS search direction display 6.1 Motivation

The pulses (transmit pulses) of the 457 kHz transmit-LVS signal have a period of the order of 1 second in known transceivers (see ETS 300718). For the display on the conventional WMS in the search mode, this means that the direction indicator is only updated approximately every second. Leads the User with his avalanche turn through, this can temporarily indicate an incorrect search direction. This may hinder the efficient search of victims. Compass-based interpolation of the search direction indicator can mitigate this problem.

6.2 Idea overview

1. 1. The transceiver is equipped with an electronic compass (also called magnetic field sensor or H-sensor).
2. 2. This compass captures the relative rotation of the avalanche transceiver.
3. 3. This information interpolates the direction indicator of the transceiver in search state between two 457kHz LVS pulses.
4. 4. This information interpolates the LVS orthogonal direction indicator in the "seek" state in the "fine search phase" between two 457kHz LVS pulses.
5. 5. The compass is used as the second sensor to detect the high movement condition (see Chapter 2).

6.3 Realization 6.3.1 Description of the device

1. 1. The determination of rotations is realized with an electronic compass.
2. 2. An electronic two-axis or three-axis compass is used.
3. 3. The electronic compass is fixed in the avalanche transceiver.
4. 4. A suitable, currently available two-axis electronic compass is, for example, Honeywell's HMC1052.
5. 5. If necessary, the third axis can be realized with a separate component, for example Honeywell's HMC1041Z.
6. 6. These components are mounted on an electronic circuit board of the avalanche transceiver.
7. 7. The electronic compass provides an analog signal for each axis.
8. 8. This signal is amplified by an analog amplifier and then digitized with an A / D converter.
9. 9. It can, for. B. an integrated microcontroller A / D converter can be used.
10. 10. The evaluation of the signal is realized in the microcontroller. Description of the method (realized as software, for example); see chapter 6.3.2
11. 11. Connection of two-axis compass (x / y axes):
    
    The signals MAG_X and MAG_Y are fed to the A / D converter inputs of the microcontroller.
12. 12. Connection of uniaxial compass (z-axis):
    
    The signal MAG_Z is fed to an A / D converter input of the microcontroller.

6.3.2 Description of the procedure

1. 1. The procedure described here is activated in the WMS in the "Search" operating state.
2. 2. Immediately after a 457kHz transmit transmit pulse is detected, the WMS will determine the orientation currently indicated by the electronic compass.
3. 3. This alignment does not necessarily have to be related to the absolute orientation of the avalanche transceiver. North match.
4. 4. This orientation will be used as the reference direction until the next 457 kHz transmit transmit pulse arrives.
5. 5. Periodically, z. B. every 100 ms, the current rotation is determined relative to the above reference direction with the electronic compass.
6. 6. The search direction display of the WMS can now z. B. updated every 100 ms. The displayed direction is in each case the search direction determined with the last 457 kHz LVS pulse, plus the above-determined relative rotation to the reference direction.
7. 7. When the next 457 kHz transmit transmit pulse arrives, a new interpolation cycle begins at point 2.
8. 8. Since this method only works with relative rotations, a (usually expensive) calibration of the electronic compass can be dispensed with.

6.3.3 Feasibility

The presented facility was implemented and tested with a prototype. The test results show that the accuracy achieved is sufficient for the implementation of the method described.

7 main switches for avalanche transceivers 7.1 State of the art

A simple and intuitive main switch is designed to facilitate efficient operation and to erroneously minimize incorrect switch settings.

7.2 idea

• ■ alle Forderungen des LVS-Standards ETS 300 718 vollumfänglich erfüllt
• ■ mit Handschuhen bedienbar ist
• ■ dank einem transparenten Teil das Licht der LED, die zur optischen Kontrolle des Sendestatus des LVS dient, auf die Geräteoberseite bringt und damit eine einfache Kontrolle der Funktion "Senden" erlaubt, auch wenn das Gerät im Tragsystem untergebracht ist.

The WMS is provided with a switch which

• ■ All requirements of the WMS standard ETS 300 718 fully met
• ■ Can be operated with gloves
• ■ thanks to a transparent part, brings the light from the LED, which visually controls the transmission status of the transceiver, to the top of the device, allowing easy control of the "transmit" function, even when the device is in the carrier system.

7.3 Description of the device

1. 1 Schieber
2. 2 Zusätzlich zur Entriegelung (3) eine Entriegelungstaste, die durch Drücken das Verschieben des Schiebers von der Position SEND zu OFF ermöglicht
3. 3 Entriegelungstaste, die durch Drücken und gleichzeitigem Schieben den Schalter von OFF zu SEND, von SEND zu SEARCH und zurück ermöglicht
4. 4 Schieberteil, der jeweils auf der Seite OFF und SEARCH vorsteht, wenn auf die jeweilige Position gestellt wird.

1. 1 slider
2. 2 In addition to the release (3), there is a release button which, when pressed, allows the slide to be moved from the SEND position to the OFF position
3. 3 Release button, which, by pushing and pushing at the same time, enables the switch from OFF to SEND, from SEND to SEARCH and back
4. 4 Slide part protruding on the OFF and SEARCH sides respectively when set to the respective position.

OFF position:

In the OFF state, the slider is positioned on the left side. Here is a part of the slide (4) before (signal element), so that the user of the WMS this part in a disturbing way reminds that the device is not turned on. If enough pressure is applied to the protruding part in the direction in which the slider moves, the switch can be set to SEND. This could be beneficial if someone gets into an avalanche but has not turned on their device yet. As a result of the turbulence during an avalanche release sufficiently high pressures on the protruding slide part, the device could still be turned on.

From the OFF position, press the release button (3) and simultaneously move to the SEND position. A lock prevents you from accidentally getting to the SEARCH position.

Position SEND:

This switch position is the most common condition when using the WMS. In the SEND position, a pulsing LED indicates that the device is activated. The light from the LED is displayed to the outside via the release (3). Therefore, the release (3) is transparent / semitransparent designed. By pressing the release button (3) again, the switch can be set to SEARCH. If, however, SEND is set to OFF, the release (2) must also be pressed so that the avalanche safety device can not be switched off by mistake.

Position SEARCH:

In position SEARCH a part of the slide (4) is analogous to the position OFF. (Signal element) This should alert the user that the device is not in the usual SEND position. As in the OFF position, the SEARCH position can be set to SEND by pressing the protruding part (4) in the direction in which the slider moves.

The dimensions as well as the forces for the unlocking are chosen such that the switch can be operated with gloves. On the two preceding parts, in addition to the clarification of the switch positions, the respective switch positions are labeled.

Thus, all the requirements of the avalanche transceiver standard ETS 300 718 can be met, in addition to the operability with gloves, which can be very useful when used in wintry conditions.

Claims (53)

Search device, in particular an avalanche victim search device, characterized in that the search device has sensor means for determining a movement state of the search device. Search device according to claim 1, characterized in that the sensor means comprise an acceleration sensor, in particular a three-axis acceleration sensor, wherein the acceleration sensor is fixedly mounted in the search device. Search device according to one of claims 1-2, characterized in that the sensor means are designed such that the movement state "much movement" can be determined, in which a movement of the search device is above a high threshold value, so that the movement state "little movement" is determinable, in which a movement of the search device is below the high threshold and above a low threshold and that thus the movement state "no movement" can be determined, in which a movement of the search device is below the low threshold. Search device according to one of claims 1-3, characterized in that it comprises a transmitting device for transmitting its own transmission signal and is designed such that a transmission power of the transmitting device is adjustable depending on the movement state of the search device, wherein in the state of motion "a lot of movement" the transmission power the transmitting device can be reduced, in particular reduced to a minimum value. Search device according to one of claims 1-4, characterized in that it comprises a transmitting device for transmitting its own transmission signal, wherein the own transmission signal comprises a transmitted with a certain period transmit pulse of a certain frequency and the search device is designed such that, depending on the state of motion of the search device has a pulse duration of Transmit pulse of the own transmission signal is adjustable, wherein the period is in particular of the order of one second and the particular frequency in particular in the range of 457 kHz. Search device according to claim 5, characterized in that it is designed such that, depending on the movement state of the search device, a temporal position of the transmission pulses of the own transmission signal is variable. A search device according to any one of claims 1-6, characterized in that it comprises a receiving device for receiving a transmitted from another search transmitter signal, is operable in a transmit mode and in a search mode, wherein in the transmit mode, the own transmit signal and the search mode of the other Search device emitted transmission signal is receivable, wherein the search device is designed such that it is automatically switched between the transmission mode and the search mode depending on the state of motion of the search device. Search device according to one of claims 1-7, characterized in that it is designed to be portable, so that it can carry a user, and with the sensor means, a vital state of a user carrying the search device is determinable. Search device according to one of claims 1-8, characterized in that the acceleration sensor supplies a time-resolved output signal and the search device comprises a microprocessor for evaluating this output signal. Search device according to one of claims 8-9, characterized in that the search device comprises a memory for storing information about the vital state of the user. Search device according to one of claims 8-10, characterized in that the search device display means, in particular a display, for displaying stored in memory or determined with the sensor means information about the vital state of the user. Search device according to one of claims 8-11, characterized in that the sensor means are designed such that at least one of the following vital functions of the user is detectable: a heart pulse, a pulse in a blood vessel, a respiration or a muscle movement. Search device according to one of claims 8-12, characterized in that it comprises communication means for the wireless transmission of information about the vital state of the user to a device equipped with a corresponding receiving device. Method for determining a movement state of the search device with a search device according to one of claims 1-13, which comprises a three-axis acceleration sensor, characterized in that a) an acceleration value in three different spatial directions is determined with the acceleration sensor at a predetermined sampling rate b) one common sample is formed from the three acceleration values by the three acceleration values being preferably added together, c) filtering the samples with a high-pass filter, in particular a digital high-pass filter, d) the filtered samples are demodulated, in particular rectified, preferably by reversing a sign in the case of negative samples, e) a running average of the demodulated samples is formed, in particular with a low-pass filter such as a digital low-pass filter, and f) the movement state of the search device is determined by periodically comparing the running average with a movement threshold. A method according to claim 14, characterized in that the search device, the movement state "much movement" is assigned, if the running average is greater than the movement threshold, the search device, the movement state "little movement" is assigned, if the running average lower than that Movement threshold is assigned to the search and the movement state "unknown", if the search device no other state of motion can be clearly assigned. Method according to one of claims 14-15, characterized in that for determining a vital state of the user, the running mean value is compared with a vital threshold value, wherein the user is assigned the vital state "sign of vital signs" if the running average is greater than the vital Threshold value and the user is assigned the vital state "unknown" if the running mean value is smaller than the vital threshold value. Method according to one of claims 14-16, characterized in that for determining a combined movement vital state of the user including the search device, the running mean value is compared with the movement threshold value and the vital threshold value, the user including the search device having the combined movement vital state "little movement, vital signs present" is assigned, if the running average is greater than the vital threshold but smaller than the movement threshold and the user together with the search device, the combined motion vital state "no movement, no sign of life" is assigned, if the running average is less than the vital threshold. Method according to one of claims 14-17, characterized in that a cardiac pulse rate is determined from the demodulated samples by a) the demodulated samples are filtered with a bandpass filter, the bandpass filter in particular allowing frequencies in the range from about 0.1 Hz to about 3 Hz to pass, b) a frequency spectrum analysis of these bandpass-filtered samples is used to determine an amplitude spectrum, the frequency analysis being carried out in particular using a Fast Fourier Transformation, and c) the heart pulse rate is determined by determining a frequency with the maximum amplitude in the amplitude spectrum. Method according to one of claims 14-18, characterized in that a plausibility check is carried out, which comprises at least one of the following criteria: d) the cardiac pulse frequency determined in this way has a plausible value, e) the associated amplitude has a plausible value and / or f) the vital state of the user is set to "sign of life", where the cardiac pulse rate is declared "valid" if the plausibility check was successful and the heart rate is otherwise declared "unknown". Search device, in particular an avalanche victim search device, with a transmitting / receiving device for transmitting its own transmission signal and for receiving a transmitted by another search transmitter signal, characterized in that the search device in addition to the transmitting / receiving device comprises communication means for wireless communication with a second search device wherein the communication means preferably comprise a short-range radio system such as a single-chip SRD transceiver. Search device according to claim 20, characterized in that the communication means are designed for communication by radio, wherein the communication means comprise transmitting / receiving means for transmitting or receiving signals with suitable for transmission in snowy terrain and through a snow cover through suitable carrier frequencies, in particular for signals with carrier frequencies in the range of 433 MHz, 868 MHz or from 902 MHz to 928 MHz. Search device according to one of claims 20-21, characterized in that it is operable as a repeater, wherein a signal emitted by the second search device, with the communication means received signal with the communication means substantially unchanged to a third search device is forwarded. Search device according to one of claims 20-22, characterized in that with the communication means an identification signal can be sent or an identification signal of another device can be received, wherein the identification signal comprises in particular a periodically emitted pulse and information for identifying the corresponding search device. Search device according to claim 23, characterized in that the transmission signal comprises a transmitted with a certain period transmission pulse of a certain frequency and the identification signal is time-coordinated with the transmission pulses and a pulse duration of the pulse of the identification signal is substantially smaller than a pulse duration of the transmission pulse of the transmission signal,
wherein the pulse duration of the pulse of the identification signal is in particular of the order of magnitude of 2 ms, the period of the transmission pulse in particular of the order of one second and the frequency of the transmission signal is in particular in the range of 457 kHz. Search device according to one of claims 20-24, characterized in that with a second search device information about a third search device exchange and / or can be signaled on the search device. Search device according to one of claims 20-25, characterized in that with the second search device with the help of the communication means information about a movement state of the search device, a vital state of a user of the search device, an operating mode of the search device or a distance or an alignment between the two search devices can be exchanged and selectively signaled on the respective other search device, in particular with the aid of corresponding display means can be displayed, are. Search device according to claim 26, characterized in that it is designed such that, taking into account the information received by the communication means, a movement state of the search device and / or a vital state of a user of the search device, the user of the search device these information or information about these indications are signaled , an operating mode of the search device is automatically changeable and / or a transmission power of a signal transmitted via the transmitting / receiving device or the communication means is adjustable, in particular reducible. Search device according to one of claims 20-27, characterized in that the communication means are designed for communication with a data processing device, wherein with the data processing device data for a parameterization of the search device, data for a software update of the search device and / or data for testing the search device are interchangeable. Search device, in particular an avalanche transceiver, with a transceiver for transmitting its own transmission signal and for receiving a transmission signal transmitted by another search device, wherein the transmission signals comprise a plurality of each transmitted with a certain period transmission pulses of a certain frequency, characterized in that the search device has coordination means for coordinating a time position of the transmission pulses of the own transmission signal with a temporal position of the transmission pulses of the other search device. Search device according to claim 29, characterized in that the coordination means are designed such that a coordination of the temporal position of the transmission pulses in dependence of a movement state of the search device and / or a vital state of a user of the search device is feasible, the coordination of the transmission pulses is exclusively feasible when the searcher is in a "much motion" state of motion. Search device according to one of Claims 29-30, characterized in that the coordination of the transmission pulses can be carried out by other search devices on the basis of the transmission signals received by the transceiver. Search device according to one of claims 29-31, characterized in that the search device in addition to the transmitting / receiving device comprises communication means for wireless communication with other search devices, wherein the coordination of the transmission signals due to transmitted with the communication means data is feasible. A method for transmitting a transmission signal for implementation with a search device according to any one of claims 29-32, wherein the transmission / reception device, a transmission pulse of a certain frequency is emitted with a certain period, characterized in that a temporal position of the transmission pulses of the own transmission signal with a temporal position of the transmission pulses of the transmission signal of another search device is coordinated. A method according to claim 33, characterized in that one of the own transmit pulses is omitted and the searcher in a corresponding time interval, the transmitting / receiving device is switched to receive, wherein a temporal position of the own transmission pulses is maintained, if it is determined that no other search device in this Time interval transmits its transmission pulses or that the temporal position of the own transmission pulses is shifted if it is determined that another search device transmits its transmission pulses in this time interval. A method according to claim 34, characterized in that , if it is determined that another search device transmits its transmission pulses in this time interval, the search device omits another transmission pulse and determines whether another search device still transmits its transmission pulses in this time interval and the search device only shifts the temporal position of one's own transmission pulses, if this is the case. Method according to one of claims 34-35, characterized in that the search device shifts the time position of the own transmit pulses by an integer multiple of a pulse duration of a transmit pulse, wherein it is preferably determined by a random generator to determine what an integer multiple of the pulse duration the temporal position the transmission pulses is shifted. Method according to one of claims 33-36, characterized in that it is determined with a random generator, which transmission pulse is omitted, wherein the random number generator, in particular with a hit rate of about one to twenty decides whether a transmission pulse is omitted or not. Method according to one of claims 33-37, characterized in that the search device exchanges information with other search devices about their identity, a temporal position and a pulse duration of the respective transmission signals by means of communication means provided in addition to the transceiver a database stores on the basis of the information in the database determines whether another search device sends out its transmission signal in this time interval and possibly shifts the position of their own transmission pulses based on the information stored in the database. Search device, in particular avalanche victim search device, with a manual switch, characterized in that the handset comprises a force acting on a housing outside of the locator adjustment mechanism with at least three adjustment positions, wherein in a first setting the search device is switched on and off, in a second setting position on transmission and in a third on reception, ie search is switchable and all switching positions are lockable. Search device according to claim 39, characterized in that the handset comprises a large area, provided with grip elements unlocking button, which is also operable with a glove-clad fingers, wherein the adjusting mechanism is adjustable only when the unlocking button unlocked. Search device according to claim 40, characterized in that the manual switch comprises a locking button with which the adjusting mechanism can be blocked together with the unlocking button, wherein the handset is designed such that the locating device can be switched off only with simultaneous unlocking of the locking button and the unlocking button. Search device according to one of claims 39 to 41, characterized in that the adjusting mechanism is designed as a linear slide. Search device according to one of claims 39 to 42, characterized in that the manual switch comprises a first mechanical, projecting over the housing surface signal element for indicating an off state of the locator and comes to rest in the on state within the housing, wherein the hand switch is preferably designed in that, after overcoming a predetermined securing force, the signal element can be pressed in for switching on, the manual switch comprises a second mechanical signal element protruding beyond the housing surface, which indicates a search state of the search device and a transmission state lying in the housing indicates the seeker, wherein the hand switch is preferably designed such that the second signal element after overcoming a predetermined securing force for switching between search and send state can be pressed, wherein the two signal elements at separate locations of the housing exterior, in particular on opposite sides of the housing, are arranged , Search device according to one of claims 39 to 43, characterized in that the hand switch comprises a lighting element which lights at at least one setting position, in particular in the send setting position, wherein the adjusting mechanism preferably has a transparent region, which in relation to the lighting element in such a way is arranged that this is in the transmit setting position on the lighting element. Search device, in particular an avalanche victim search device, having a receiving device for directionally receiving a transmitted signal from another search device and for determining a receive direction of the transmit signal, wherein the transmit signal comprises a transmitted with a certain period transmit pulse of a specific frequency, characterized in that the Search device display means, in particular a display, and a position determining unit for determining a position of the search device, in particular a magnetic field sensor such as an electronic compass, wherein the search device is designed such that at a measuring time substantially simultaneously with the receiving device, the receive direction of the transmission signal and the position of the search device can be determined with the position determination unit, wherein the position of the search device can be determined in particular relative to the receive direction of the transmission signal. Search device according to claim 45, characterized in that it comprises a memory unit for storing the reception direction of the transmission signal and the position of the search device and a processing unit, wherein with the Processing unit from the stored receiving direction, the stored position of the search device and an instantaneous position of the search device relative to the stored position of the search device, a current direction indicator for signaling with the display means is calculated. Search device according to claim 45 and one of claims 1 to 13, 20-32, 39-44 or 46, characterized in that the sensor means for determining a movement state of the search device comprises the position determination unit. Antenna unit for a short-range radio system, in particular an SRD radio system, wherein the antenna unit for two separate, different frequencies can be used, characterized in that the antenna unit for each of the two frequencies has a resonance point and in particular acts as a transmitting and receiving antenna. Antenna unit according to claim 48, characterized in that it comprises a supercritically coupled, two-circuit bandpass filter for the two frequencies, which acts as a matching circuit. Antenna unit according to claim 49, characterized in that the antenna is designed as a loop antenna, a first circle of the bandpass filter is formed by the loop antenna and at least one capacitor in series and a second circuit of the bandpass filter by an inductance with at least one capacitor connected in series, and both circuits are capacitively coupled. Antenna unit according to claim 50, characterized in that it comprises a switched to the inductance of the second capacitor capacitance, via which a transmission signal einkoppelbar- or a received signal can be coupled out. Antenna unit according to one of claims 50-51, characterized in that it comprises a printed circuit board on which the inductance of the second circle, the loop antenna and the capacitors are arranged, wherein the inductance are in particular formed as a wire loop and the loop antenna in particular as a metallic stamped part. Search device according to one of claims 13, 20-28 or 32, characterized in that the communication means comprise an antenna unit according to one of claims 48-52.