When it comes to SIM cards many of us hold a perception of small plastic and metal objects that we need to have in our phone for it to work, and we give them little further thought. Most of us don’t realise how genuinely interesting these apparently mundane objects actually are. Luckily for you this QI style post is about to help you discover the most amazing facts about SIM cards so you can impress your mates the next time your battery dies, and you find yourself swapping SIMs to make a call.
Q. How many different SIM card size variants are there?
A. You probably guessed that there are three different sizes of SIM card: Standard SIM, Micro SIM and Nano SIM? If that’s the case, then you are incorrect. There are in fact four size variations of SIM cards. The original SIM card, which was introduced in 1982, was 85.60 mm × 53.98 mm – the same size as a credit card. It wasn’t until 1989 before we got the second incarnation (the Mini SIM) which measures just 23mm x 12mm. It is this Mini SIM which most of us incorrectly think of as the original SIM card.
Have you ever wondered why the SIM cards of today always need to be pulled out from within a much larger credit card sized piece of plastic? It’s because all new SIM cards are required to be retrospectively compatible with the earliest devices. So even today’s newest SIM cards can be inserted into a mobile phone from the 80s provided of course it’s still connected to the surrounding plastic!
Q. How much do SIM cards cost?
A. It really depends on who is paying for the SIM card, but all of the answers above are correct. Consumers in the UK can get free SIMs from any network provider. However, the Providers themselves do not get the SIMs for free. They then have to arrange production of the SIM pack wallets, which can cost around £6 each. Each SIM pack contains a branded SIM card and some printed promotional material, all of which usually comes encased in a branded cardboard wallet. The print companies buy the blank, unbranded SIM cards from the Far East, paying anything between 1p to 80p per unit depending on quality and quantity ordered.
Q. What is the most valuable part of a SIM card?
- Metal plate
- Plastic card
On a cost per micron basis the metal plate is the most valuable part of any SIM card because it is coated with a layer of gold. The gold coating is just 8 microns thick and each SIM contains more or less 1mg of gold depending on the area of the plate. On average, ten thousand SIMs would equate to 1Kg of gold.
Gold is used on the metal plate because of its conductive properties and resilience to wear. You can find the same gold plating inside your actual phone on a variety of metal connectors, including those that press against your SIM as well as on circuit boards in other electronics equipment.
Q. What information can be stored in your SIM card?
- Text messages
- Your contacts and network provider
- Last dialled history
The answer is all of the above depending on what phone you have. Although these days many of us can use our mobile phone to control whether we save phone numbers to the actual SIM, we don’t get to control what else is stored on the card. Even if you store your contacts exclusively on the phone then your text messages, network provider and last dialled number can all still be determined via the SIM. This is why forensics teams can find SIMs to be very useful in solving crimes. If your SIM is registered (as it must be by law in the UK) authorities can also associate the SIM with an individual’s name and address via the cards International Mobile Subscriber Identity (IMSI).
Q. For which of the following can a SIM card be used?
- For frying an egg in a survival situation
- Sterilizing a glass of water
- For tracking people
I really hope you didn’t actually pick answers A or B because that would just be nuts. The answer was ‘C. SIM cards can be used for tracking people through a method known as triangulation. The idea is that if you can locate the mobile, you will locate its owner. Mobile phones signal nearby masts whenever they are used and also intermittently when not in use. When three masts are signalled at the same time, positioning software can perform a calculation to discover the geographical position between the three masts that the phone is located between.
The signal that is sent from the phone contains the SIMs IMSI number followed by the network code, and finally the phones own identification number (IMEI number). With this information from a registered SIM card, authorities can identify who owns the phone, where they are located, and what phone they are using. Once this information has been gathered, even if a user replaces the SIM card, the authorities can still trace the person based on the phones ID and they can then match that to the ID of the new SIM card.
A phone does not even need to be switched on to be tracked because phones send out an intermittent signal even if switched off. The only way to prevent the signal from being emitted is to remove the battery.
I suspect now that you have read five fascinating free SIM facts you will never look at a SIM card in the same way again. Should you feel inspired enough to start pushing your SIM card to the limits remember to back up your numbers first, and please let us know how you get on! If you know of any other amazing facts about SIMs please share them with us below in comments area.