Uncovering the Science Behind SIM Card Technology

You walk around with a digital ID badge in your pocket all day, every day and you may not know it.

Part of the complex machinery that is your cell phone is that small, removable card that follows you from phone to phone. For many, these SIM cards are as important a part of modern life as the shoes on your feet.

But, how does a SIM card work? What does it do and why do we all carry them with us everywhere we go? Here is a quick lesson on what SIM cards are, how they work, and why they are so important.

What Does a SIM Card Do?

SIM cards, or subscriber identity module cards, are small plastic cards that are slid into your cellular devices. They act as your unique ID and allow your device to communicate with your cellular network.

These cards are what allow your friends and family to know it’s you calling before they answer. They also work to track your usage for billing and other necessary uses by cell companies.

Some bandwidths of cellular devices work differently. Among the differences – some communicate to the network without the need for SIM cards.

How Does a SIM Card Work?

You can think of your SIM card as a key. They identify you as a subscriber to a cellular network, allowing you access to the signals you need to make calls or connect to the internet.

Each card carries a unique signature that is “read” by the security systems on a network whenever you turn on and connect your device. The reason your card follows you from phone to phone is that your ID doesn’t change as long as you stay on a given network.

SIM Card Sizes

SIM cards come in three basic sizes. As you can imagine the first SIM cards were the largest and they have gotten smaller since then. All three sizes are still in use today for various applications.

Standard SIM Cards

Standard SIM cards date back to 1996. They are 15 x 25mm and are mostly plastic surrounding the small chip that does the work of the SIM card. These are now primarily used in older and very basic model cell phones.

Micro SIM Cards

In 2003, these smaller SIM cards were introduced to the market. They come in at 12 x 15mm, though the chip is the same size as in the standard cards.

While most phones in the last 5 years no longer use these, they are still widely used in slightly older models.

Nano SIM Cards

The newest and smallest of the sizes, these nano cards, introduced in 2012 measure 8.8 x 12.3 mm. Again, the chip itself hasn’t changed in size since first introduced. The plastic border on these cards, however, is almost nonexistent.

All Hail the SIM Card

There will come a day when newer, more effective technology comes around to replace the need for SIM card technology. It’ll likely come once you really understand the answer to the question: How does a SIM card work?

But for now, these little ID badges are sold by the billions every year and used by people around the globe every minute of every day.

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