Mobile 3G Broadband

3G Phone and Data Sim Information

Overview

The Sim card - or "Subscriber Identity Module" - used in a mobile phone, 3G Dongle, Data card or 3G enabled laptop or tablet is a small silicon chip that uniquely identifies the account and telephone number to be used by the device it is inserted into.  In short, the Sim card tells a mobile phone or other 3G Device what account it is to work with and to allow the appropriate access to make calls and use 3G data as per the account for the Sim.

Sim Card Formats

There are two common styles of Sim Card:

Standard "Mini" Sim Cards - These are commonly used in almost all devices apart from the iPhone 4, iPhone 4S and iPad 3G models and are the more familiar Sims in use today.  "Mini" Sim cards are 25mm x 15mm with one corner chamfered to indicate correct orientation.

"Micro" Sim Cards - These are about half the size of a standard Sim and were initially used only in the iPhone 4, but are now used in the iPhone 4S and iPad 3G models as well as some other devices. "Micro" Sim cards are 15mm x 12mm with one corner chamfered to indicate the correct orientation.

Some early devices and also some larger satellite telephone use a "Full Size" Sim - this is a credit card sized Sim, 85.6mm x 53.98mm.  This is also how Sim cards are delivered to end users, with pre-scored cut-outs in the card to allow the smaller Mini or Micro Sim format to be popped-out of the larger, easier to handle card.

In each case the contacts on the Sim card have the same function and layout - but the plastic carrier simply enlarges the Sim card to suit the required format for the device it is inserted into.

It is therefore possible to "convert" the larger "Mini" Sim to the "Micro" Sim format simply by very accurately cutting it to the correct size, with the correct position of the contacts and the chanfered corner.  This is much more easily done with a tool designed for the purpose and these are readily available and are often supplied with adaptors to allow the cut-down Micro-Sim to be used in the larger Mini-Sim slot when required.

Types of Service

Far more important than the form factor of a Sim is the services and call and data costs associated with the account it is tied to.

Many phone contracts do not include data usage and charge large amounts for any data used by Internet or Email access, so putting a mobile phone Sim in an iPad, Tablet or 3G modem may be very expensive to use.  A 3G Data Sim will almost always work out much cheaper.

Also - most operators still have much higher charges when a phone or 3G device is "Roaming" - i.e. outside of the country it is designed to operate in.  These roaming charges can be VERY high and it is generally advisable to disable 3G Data roaming by default and to check the cost of making and receiving calls before going abroad.

Saving money on charges when abroad

By planning ahead and checking call charges before travelling, you may find it cost effective to look at either a specific "Country Sim" for where you are travelling to - or an "International Sim" if travelling to multiple countries.  These are purchased before travelling and replace the Sim in your handset or other device, allowing you to let people know what number you can be contacted on when abroad.

 

If you have experience (good or bad) with International or Country Sims, please drop us an email at:

editor@mobile-3g.co.uk

We would appreciate your views on how well these work for all types of International travel - i.e. Business, Personal, Single and Multi-Country use.