"One of the main targets of the PIEPS development team was to achieve a best possible 'useful range'. All other beacons available on the market feature a more or less elliptical receiver range, that means a different range in different orientation of the receiver antenna in relation to the position of the transmitter. (best range with antennas 'face to face', worst range usually if antennas are angled by 90°)....The PIEPS DSP is optimized in terms of 'circular receiver range' (same range in all antenna orientations) and constant receiver range over the whole frequency range."
https://www.patrollersupply.com/equipment/item_4333.asp

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Note added at 6 hrs (2017-07-24 15:30:38 GMT)
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Here's an explanation of how they work:
"When the owner sets out on a skiing descent, the transceiver is activated, causing the device to emit a low-power pulsed beacon signal during the trip.Following an avalanche, and if the holder of the transceiver is safe and has not themselves been caught by the avalanche, they may switch the transceiver from transmit into receive mode, allowing use as a radio direction finding device to search for signals coming from other skiers' transmitter beacons who may be trapped."
https://en.wikipedia.org/wiki/Avalanche_transceiver