This does not mean that a SIM card can only connect to a maximum of 33 or 80 networks, but this means that the SIM card issuer can only specify up to that number of preferred networks, if a SIM is outside these preferred networks it will use the first or best available network.
The network operator that issued the SIM card can use this to have a SIM card connect to a preferred network in order to make use of the best price and/or quality network instead of having to pay the network operator that the SIM card ‘saw’ first. All allow a maximum of 250 contacts to be stored on the SIM, but while the 32 KB has room for 33 Mobile Network Codes (MNCs) or “network identifiers”, the 64 KB version has room for 80 MNCs.This is used by network operators to store information on preferred networks, mostly used when the SIM is not in its home market but is roaming. SIM cards can come in various data capacities, from 32 KB to at least 128 KB. The SIM also stores other carrier-specific data such as the SMSC (Short Message Service Center) number, Service Provider Name (SPN), Service Dialing Numbers (SDN), Advice-Of-Charge parameters and Value Added Service (VAS) applications. The most important of these are the ICCID, IMSI, Authentication Key (Ki), Local Area Identity (LAI) and Operator-Specific Emergency Number. SIM cards store network-specific information used to authenticate and identify subscribers on the network. The card was cropped down to 25 × 15 mm (ISO/IEC 7810 ID-000). Soon the race for smaller telephones called for a smaller version of the card. Early versions consisted of the whole full-size (85 × 54 mm, ISO/IEC 7810 ID-1) smart card. The UICC smart card consists of a CPU, ROM, RAM, EEPROM and I/O circuits.
The telephone book is a separate application and not part of either subscriber identity module. With the UMTS release 5 a new application, the IP multimedia Services Identity Module (ISIM) is required for services in the IMS. It is also possible to access a GSM network using a USIM application and it is possible to access UMTS networks using a SIM application with mobile terminals prepared for this. A UICC may contain several applications, making it possible for the same smart card to give access to both GSM and UMTS networks, and also provide storage of a phone book and other applications. In a GSM network, the UICC contains a SIM application and in a UMTS network it is the USIM application. In general, UICC is referred as “ SIM Card“ With the advent of more services, the storage space will need to be larger.
The UICC ensures the integrity and security of all kinds of personal data, and it typically holds a few hundred kilobytes. The UICC (Universal Integrated Circuit Card) is the smart card used in mobile terminals in GSM and UMTS networks.
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