And several companies had concept and prototype devices that envisioned digital cameras and global positioning system expansion devices that would fit into the SD card slot.

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In 1993, NTT DoCoMo, Japan's principal mobile-phone carrier, opted for a technical standard called Personal Digital Cellular (PDC), which was incompatible with the Global System for Mobile Communications (GSM), the standard adopted by most of the rest of the world.

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Today, they've been supplanted even further by digital compasses that use electronic sensors and devices that take readings from Global Positioning System satellites.

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