You’ve probably used a mobile phone for a very long time, meaning you understand that a SIM card gives you your phone number. But what else do you know about this little card? Believe it or not, there’s much more to your SIM card than the ability to use your phone number and store a few contacts. In addition to this, the advent of smartphones creates a new environment in which SIM cards can show an incredible amount of potential. You’ll discover that talking about these little gold-plated pieces of plastic is actually more intriguing than you thought!

What Do SIM Cards Do?

Your subscriber identity module (SIM) card is chiefly a way for your carrier to identify your relationship to it. Much like how an IMEI number identifies the hardware on your phone, the SIM card will give your carrier a way to identify you so that it can route calls in your direction.

SIM cards store different amounts of information, depending on what your carrier gives you. The number ranges anywhere from 32 to 128 kilobytes. You can’t use all that space to store contacts, though. You’ll always have a maximum of 250 contacts. This is because the card has to reserve its remaining space to store things like the short message service center (SMS-C) number (the number that gives you the ability to send text messages), the service provider name (so that the phone immediately recognizes what carrier it has to connect to by default), and other parameters that your carrier might need for your phone to function properly. Once you insert your SIM card, your phone will pull this information out and use whatever is relevant whenever it’s needed.

Perhaps one of the biggest reasons why SIM cards reserve particular areas of their memory is because they have to store a varying number of mobile network codes for roaming purposes. If you’re travelling a lot, you might not get service from your provider in particular areas. Roaming capabilities provided by your SIM card allow you to continue your conversations even without your hometown network.

Your SIM card doesn’t identify itself to a carrier using a phone number. Instead, it uses something known as an international mobile subscriber identity (IMSI) number. Using this convention, a carrier can immediately disable an old SIM card from a phone that was lost or stolen and immediately move its number (and sometimes even its contacts) to a new SIM.

What Kinds of SIM Cards Are Out There?

There are a few types of SIM cards used in regular day-to-day applications. These are found particularly inside of phones:

Mini SIM

This is your run-of-the-mill SIM card. You’ve probably grown bored of staring at it. Let’s move on.

Micro SIM

This SIM card (size comparison above) is particularly championed by smartphone manufacturers as a significant space-saving measure for phones that have to cram in as much hardware as possible. Real estate is running short, so everything is shrinking. The next SIM, though, takes the entire concept of “think thin” to a whole new level.

Nano SIM

The Nano SIM (right) is just a regular SIM with practically everything shaved off. Phone manufacturers that are desperate to cram as much hardware in as small a space as possible sometimes take these attempts to levels that require something as drastic as a Nano SIM. They’re not just annoyingly small. They’re also effortlessly easy to lose.

Sticker SIM

This isn’t a SIM card, per se, but it’s still interesting. Electronic stickers like the one KnowRoaming offers allow you to supercharge your SIM card with additional features by applying it right on top of the card. KnowRoaming’s sticker lets you have more control of your roaming rates, bypassing the middleman (your carrier) and instead choosing the lowest rates available in whatever country you travel to. When you’re home, the sticker goes to sleep and lets your SIM card handle everything.

How SIM Cards Will Work In The Future

Well, I’ve already shown you the sticker SIM. This is just one of the many ways that SIM technology is evolving. Some suggest getting rid of the concept entirely, while others suggest using the SIM card to track stolen goods (I prefer this variation).

Let’s continue this discussion. What do you think we should do with SIM cards? Are they still worth something in a world that’s so connected? Give us your opinion in a comment below!

Miguel has been a business growth and technology expert for more than a decade and has written software for even longer. From his little castle in Romania, he presents cold and analytical perspectives to things that affect the tech world.

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