Subscriber identity module (SIM),
Definition of Subscriber identity module (SIM):
Small printed circuit board which must be inserted in a GSM phone to sign-on as a legitimate subscriber and to make and receive calls. SIM holds a microprocessor that stores subscriber information (identification number, phone numbers, and personal preferences) and encrypts-decrypts voice signals making it virtually impossible to eavesdrop on somebody elses call.
Meaning of Subscriber identity module (SIM) & Subscriber identity module (SIM) Definition