Your cellphone cannot connect to a cellular provider without a SIM card installed.
A cellphone contains a Subscriber Identity Module card that stores the phone's mobile number, owner's name and account information connected to the phone. The card also stores the phone's serial number as well as any names and telephone numbers, known as contacts, that have been entered into the phone. The three types of SIM cards available for cellular phones are full, mini and micro.
Full-Size Card
Full-size SIM cards measure 85.60 millimeters long, 53.98 millimeters wide and have a depth of 0.76 millimeters. The cards look like a credit card and have metal contacts that transmit data from the card to your cellular phone at a rate of 5 megahertz. Full-size SIM cards slide into a slot on the side, bottom or inside of your phone.
Mini-size Card
Mini-size SIM cards measure 15 millimeters wide, 25 millimeters long and have a depth of 0.76 millimeters. A mini-size card contains one curved corner that helps guide it into a phone's SIM slot. The cards also contain metal contacts that interface with your phone for data transmission at a rate of 5 MHz. Mini-size cards may also be placed in a full-size card carrier for use in cell phones that require a full-size card.
Micro-size Card
Micro-size SIM cards, also known as 3FF cards, measure 15 millimeters long and 12 millimeters wide. The cards are the smallest of the three and also contain metal contacts for data transmission. Micro-size cards can work in phones that use full-size and mini-size SIM cards via a converter. Micro-size SIM cards also transmit data at a rate of 5 Mhz.
SIM Card Classes
SIM cards are divided into two classes: country-specific and international. Country-specific SIM cards only work in the country you purchased the phone in. International SIM cards work in multiple countries. Calling rates vary from country to country when using a international SIM. You can also purchase a prepaid international SIM card and use it if you travel outside of your home country on a frequent basis. Consult with your cellular service provider for information on the class of SIM card you phone is able to accept and use.
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