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How iPhone 3G S Compass Works

The document explains how the iPhone 3G S employs a magnetometer without using magnets, thus avoiding magnetic interference that could disrupt cellular capabilities. It describes the use of the AK8973 chip, which detects ultra-low frequency signals to help calculate the device's orientation and direction. The author humorously speculates about the absurdity of Apple transmitting an RF signal globally from the North Pole.

News & Politics◦Devices & Hardware◦
How the Apple iPhone 3G S Magnetometer Works.By Dr. ArsenyLebedev B.S. Ph.D
Compasses are attracted to the Earth’s poles using MagnetsSource: Everyone knows that.
The iPhone 3G S does not use magnets.
Magnetic interference would render the iPhone’s cellular capabilities useless.Sources: http://link.aip.org/link/abstract/VIRT01/v19/i22/p112/s1
http://weeksmd.com/?p=1521
http://blogs.crikey.com.au/planetalking/2009/03/06/electromagnetic-interference-back-in-frame-as-possible-cause-of-qantas-a330-incidents/
http://machinegunkeyboard.com/?p=254
http://www.macnn.com/blogs/2009/06/11/apples-iphone-emergency-mode-processor-features-patent.htmlSpectrograph AnalysisOnce introduced, magnetic interference drops signal strength parabolically. Frequency and power ranges are consistent with GSM bands.
Electronic Solution Apple must be utilizing simple RF to determine North.
Hardware DetailsThe AK8973 chip on the iPhone is a small sensor that “listens” for an ultra low frequency signal. If that signal comes from a specific spot like North, paired with the accelerometer the device can calculate its orientation and direction.Sources:http://www.appleinsider.com/articles/09/06/24/cost_to_build_apples_new_iphone_3g_s_estimated_at_179.html