How do SIM cards work?

Back in the good old days telephones had physical wires linking one end to another. This was regardless of whether or not you were making a call across the continent or just using a couple of tin cans attached to a string.

In the past whenever you have dialed a number your phone company could route your call exactly where it needed to go using cables.

But in this brave new world of not only phone calls but Twitter & Instagram and other stuff that the people are doing being blasted out from cell towers everywhere, these signals have to know where they’re going every time.

This is where SIM cards come in. SIM stands for “Subscriber Identity Module” which gives a pretty big hint as to what it does. It identifies what mobile phone subscriber is using in particular iPhone, Galaxy or a Windows phone.

And although SIM cards are quite a low capacity with many of them holding well under a megabyte of data, the small amount of information that they do hold is extremely important if you want your phone to be of any use.

SIM cards store a 64-bit number that serves as a unique identifier code and although that only takes up 8 bytes of storage, there are over a 9 quintillion unique numbers that can be stored in this way on a single SIM card. So this method should work no matter how many people register with a particular telecom service provider.

So how does it work?

When you turn on your phone and first connect to the cell network, your phone will pass your SIM card’s ID number along with an authentication key found on the SIM card to your telecom service provider.

Your service provider then generates a random number and uses the key to spit out a response number at the same time, that random number is sent back to your phone and the same calculation is done with authentication key to generate another response number.

If the two numbers match, your service provider will recognize this and connect your phone to the network both ensuring that it’s actually you that’s connected to keep your data safe and to see who you are.

But other than just identifying information, SIM cards can also store phonebook information and although that might seem like a dated concept in an age where phones can store almost anything you can think of, on internal memory or separate expansion cards.

This was important when things like basic mobile phones/flip phones were more popular so you wouldn’t lose all of your contact info when upgrading it or if you’re not storing your phonebook with a Google or Apple cloud service.

If you are moving SIM cards between phones just make sure that they are the same size, as there are different SIM form factors.

Some mobile phones have their authentication information on built-in internal memory instead.

Of course, while SIM cards are quite useful when you want to switch phones, this isn’t always possible because of something called SIM locking.

You see phones you get from a major carrier with a service contract are often locked, meaning they will only work on that carrier’s network.

Service providers do this so they can subsidize the cost of the phone allowing you to get higher-end equipment for a much lower price because they know they will be getting money from you for a certain time due to your subscription contract.

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Fast Charging - How does it work?

Chances are that you don’t give more than a few seconds of thought each day to charging your phone. Hopefully, you remember to do it before you go to bed and that’s about it right.

What if you just kind of passed out after a night of heavy drink & woke up the next day realizing you forgot to plug it in and you have to leave the house in half an hour.

Enter fast charging, a feature that is supported by some modern phones and tablets that you power it up in the time that it takes no more than a shower or having breakfast.

The reason many devices take such a long time to charge normally is the limited amount of power many common wall chargers push to your phone or tablet at once, typically 5Watts or less.

This is a design choice that keeps manufacturing costs low and also ensures that the relatively small batteries inside of mobile gadgets won’t fry from being overloaded with too much power.

But in reality, many mobile devices can handle more than this thanks to internal circuitry that sets a maximum amount of wattage that will hit your battery at one time.

Fast chargers take advantage of this by adjusting the voltage, amperage or both to deliver up to 20 watts or even higher if your device supports the technology.

But what needs to be supported?

We are just clobbering a battery with electrons well there are a lot of other factors but the most basic one is that “with the higher power, comes higher heat”.

So a device without enough internal room for the battery to expand might end up damaged if it gets charged too quickly. So for that reason, many companies that developed fast charging technology have implemented a handshaking process between the chargers and mobiles/tablets to make sure they are both certified to support the extra power.

Samsung’s fast charge and One Plus’s DASH charge are both popular protocols but perhaps the most widespread one is Qualcomm Quick Charge, which is found in a large number of Android devices.

So this means that just because the charger says it supports 2.5 Amps at 5 volts, doesn’t necessarily mean that it will charge your phone super fast. Although many devices that support fast charging do come with compatible chargers, you will pay a premium for extra ones.

And you might need to buy slightly nicer cables too as cheap thin 28 gauge cords often can’t handle the extra current very well.

Also, remember that as we mentioned fast charging can generate more heat which is harder on your battery and may shorten its longevity. A real concern now that so many phones are very difficult to open if you want to put in a new battery.

Plus fast charging is much more useful when your battery is significantly drained and you need a really quick partial charge to keep you afloat for a little while.

Speeds tend to taper off significantly as your phone gets closer to 100%, unlike the charging speed you get from 0 to 50%.

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