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Question: There are a bunch of symbols and numbers on the backs of iPhones. I know what 16GB means; what about the rest?

A jumble of symbols have been trying to communicate with us from the back of the iPhone since it launched, and indeed, from a number of other non-Apple communication devices. What distinction do they mean? Compatibility with different radio frequencies? Recyclability? Edibility?

The truth is a bit more boring. Most of these symbols indicate only that the iPhone has received approval to use the various frequency spectra reserved for mobile and wireless communications and that it has passed various safety checks. We dove into hundreds of pages of regulations to see what the iPhone's various tramp stamps mean.

This symbol, an F and a C nested within a C, confers the approval of the US Federal Communications Commission. Looking through all of the stipulations the FCC places on gadgets, its heart is not easily won—everything from the the output power of the directional beams of an antenna system to what radio bands it can operate in is covered. The FCC appoints a number of Telecommunications Certification Bodies (TCBs) that can review and grant applications for FCC certification. Not all TCBs handle all kinds of devices, but if the device isn't FCC-approved, as you might guess, it has no business in the United States.

The iPhone also carries an FCC ID, another indicator that it's gotten the FCC's approval for operation. The FCC ID consists of a three-letter grantee code (Apple's is BCG) followed by a model number.

The next symbol, a garbage can with an X through it, indicates compliance with the WEEE (Waste Electrical and Electronic Equipment) Directive. The WEEE Directive is upheld by 27 states in the European Union and represents their desire that devices like the iPhone be disposed of in an environmentally friendly way, rather than thrown in the trash as electronic waste.

The EU is so passionate about e-waste that it not only puts the symbol on devices, but it has been moved to artistic expression: as part of their effort to draw attention to the e-waste issue, the Royal Society of Arts in the United Kingdom created "WEEE Man," a 23-foot, 3.5-ton sculpture meant to equal the amount of e-waste a person in the UK will create over the course of a lifetime.

The WEEE symbol is often mistaken for representing compliance with the Restriction of Hazardous Substances (RoHS) Directive, which mandates that manufacturers provide a way to dispose of products' toxic parts, like batteries. The RoHS doesn't have a representative symbol, but Apple and the iPhone are still subject to its regulations.

The next symbol is called the "CE mark." It used to stand for "Conformité Européene" but now just works as the general stamp of approval for a product's sale in the European Union. The CE mark indicates compliance with all relevant directives that govern things like voltage and frequency band use. Companies can self-certify for some of the rules, like those concerning electromagnetic compatibility and interference. A product's ability to meet other directives, though, must be certified by an accredited testing firm.

A number next to a CE mark on a device indicates that the manufacturer used a notified body (an organization accredited to evaluate CE compliance) to make sure their product meets CE standards. In this case, notified body 0682 points to Cetecom ICT Services, a firm accredited by Germany to evaluate for CE directives. Cetecom would likely have evaluated the iPhone for its compliance with the telecommunications terminal equipment directive, one of those things that companies can't self-certify.

The exclamation point is known as the "alert symbol," and it supplements the other CE markings. States in the European Union have restrictions on various frequency bands—for example, a wireless device being operated outdoors in France can only use frequencies between 2.4 GHz and 2.454 GHz. When a device can follow all these restrictions, it is said to work on "harmonized frequency bands" and is called a Class I device. When it doesn't, like the iPhone, it is a Class II device and must carry the extra alert symbol so that users know the phone might try and operate on frequency bands it isn't allowed to use in certain countries.

"IC ID" on a device stands for "Industry Canada Identification", and indicates that a device meets all requirements for a Category I device. These include a number of radio standards specifications (RSS), and like the other certifications it has a lot to do with how the device operates on different radio bands. For instance, mobiles must use the band between 824 MHz and 849 MHz to transmit, with a standard channel size of 30 kHz.

Devices that comply get an IC ID, with the first four digits (579C, in the iPhone's case) identifying the company and the remaining digits identifying the product (on the iPhone, the last digits of the IC ID are a more specific version of the model number Apple uses). Equipment that only generates interference, like some passive radio devices, is classed as Category II and is deemed safe for use in Canada if it meets the standards of the FCC in the US.

This only covers the iPhone that is authorized to operate in the US, Canada, and Europe. iPhones manufactured for distribution in other countries may have a completely different set of certifications printed on them (some devices, like the Kindle, slap every regulatory stamp they get on the back so they have one version that can ship anywhere). All the rest of the iPhone's compliance medals that we didn't discuss here can be viewed in the device's Settings menu (General > About > Regulatory), along with the names of the countries that use them.