A guide to SIM cards, the small chips that connect your phone to a cellular network

A SIM card, or subscriber identity module, is a small card in your cellphone that lets you place phone calls, send text messages, and more.
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SIM cards were once the size of a credit card; learning these facts will make your head spin.

Many smartphones today no longer require a physical SIM card, but once upon a time, SIM cards were the size of credit cards. This began in 1991. If you've used a mobile phone, you're likely familiar ...