What is a sim card?

Simple! Its that bit of card with the gold bit on that we have to try and get in the slot under the battery!

Seriously though, simcards are a vital part of our mobile technology. The Sim card, or Subscriber Identity Module, allows us to identify ourselves to the mobile networks via a handset. Similarly, this simple to use, plug and play style technology allows us to swap our mobile account between handsets by imply removing the sim card (aka sim) from one phone and sticking it into another. Sometimes we might need to unblock the phone from a different network, but the underlying principle is simple.

The chip mounted on a sim card was once a unique sight, and few people had seen them elsewhere - however today things have changed and the chips are all over the place, not least embedded in our credit and debit cards, to support chip and pin technology.

A standard sim card will contain a 19 digit code, identifying such things as the country, network, dat of manufacture, the sim id itself and a check digit which helps to prove accuracy.

So there you go - a brief explanation of the simple sim!