Definition of SIM Cards

When we acquire a telephone mobile, regardless of whether it is new or second-hand, it does not come pre-programmed with a specific phone number, but we are the ones who enter the number (along with the possibility of more data) through what is called a SIM card or one of its variants. But what exactly does a SIM contain?

SIM (subscriber identity module) consists of a physical smart card with a standardized format in which the data identifying the subscriber or subscriber of the line is stored

and that, therefore, allows transferring the number of a terminal towards another.

SIM cards have evolved over time, both in size and in benefits, but both parameters in reverse: while the size has been getting progressively smaller, the benefits have been increasing.

I still remember the first cell phone I had, which mounted one of the first SIMs,

consisting of a cardboard the size of a credit card, but which already had the marks to cut the mini SIM, which is the considerably smaller card and which today we all know, mistakenly, simply as SIM.

This "cardboard" that surrounds the chip with the contacts is nothing more than insulating material that prevents short circuits.

The mini SIM measures 25x15 mm and, like all cards of this type,

In addition to maintaining the identity of the subscriber of the line, they can also store a series of data, such as contacts from the phone book.

That is why, when we configure the new smartphones, the terminal us question if we want to save the contacts on the SIM card, or on the memory of the phone (now they are used to saving also online synchronized with the phone, and in the account of the Username, as in the case of Android, in which they are synchronized with the Google account and shared with Gmail.

They also contain the configuration data for Internet access.

such as the APN access point name (Access Point Name), Username and password.

If the credit card size SIM card was inserted in a terminal of considerable size, for mini SIMs, with a slot or a small There was enough space, and with the decrease in size, the necessary space for this element has also decreased, with which they have emerged

terminals with dual SIM (capable of storing and managing two lines) or even -although much rarer- those with triple SIM

The next evolution It was

The 15x12 mm micro SIM, which has been in use since the late 1990s in electronic devices such as power meters, but has been used in approximately 2010 smartphones.

Although the contacts of the chip are the same as in the case of the SIM and the mini SIM, their appearance is different, being the same that will arrive at the nano SIM.

Thanks to their superior features, they facilitate the adoption of new technologies such as electronic payments. And although there were already other devices that used SIM cards for voice and / or data communications outside of cell phones, with the micro SIM tablets and computers with 3G and later 4G connectivity began to become popular, which included a slot for one of these cards.

The micro SIM was followed by

nano SIM, which has a size of 12.30x8.80 mm and is even less thick than the previous ones, 0.67 mm compared to 0.76 for the others.

Introduced in 2012, it maintains the same contacts as its predecessors but removes almost all the insulating material as previously. we were around it, leaving it in a minimal coating, so that what we see is only the chip with the contacts.

There are adapters, basically cardboard, that allow us to use a nano SIM in a slot micro SIM, and one of these in a slot mini SIM, although it is best to have the appropriate card size for our phone.

After all this evolution in which the size has decreased, only one step remains:

the eSIM or electronic SIM, which is nothing more than storing the SIM information on a chip of the same terminal,

Although this seems a contradiction with what I have explained, since the origin of the SIM is in unlinking the subscriber information from the physical terminal line, the eSIM involves various advantage.

The main one is perhaps the end of the reign of cell phones linked to a single operator, and skipping the limitation of one or two numbers per terminal, since we could have the information corresponding to several numbers (five, six, ten,... the space of storage on the chip is the limit) on a single phone.

ESIM already exists but has not yet been implemented, with nano SIM currently being the standard.

Photos: Fotolia - Ztudio_neosiam / Andrey Popov

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