I am not very familiar with RECCO‘s Avalanche system, but from what I gather from reading the company’s Web site, it is not an RFID system.
It appears that the detector sends out a low-frequency (LF) signal—457 kHz—that can penetrate the snow. It reflects back a signal, but it does not send back a serial number. If two skiers were buried in an avalanche, the system could pinpoint their location based on the direction of the signal coming back from the reflector worn by one of the skiers, but it could not distinguish between the two individuals (thus, there are no privacy issues with embedding the reflectors in clothing).
The system has a longer read range—200 meters (656 feet)—than passive RFID systems, because the reflector is optimized to reflect back as much energy as possible. An RFID system, by contrast, requires that a tag use energy to power a chip and modulate and demodulate the antenna to send a serial number.
—Mark Roberti, Editor, RFID Journal
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