A GSM/GPRS/EDGE wireless radio

The Mobile Switching Center is the primary service delivery node for GSM, responsible for handling voice calls and SMS as well as other services. Most GPRS devices also have the capability of using services provided by the MSC (e.g. voice, SMS, USSD). For this reason, a GPRS device will normally first register on an MSC, known as GSM registration, before attaching to the local SGSN.

Mobile Station ISDN number. This is the full phone number of a subscriber, including the national country code (e.g. 1 for US, 44 for UK, etc.). The purpose of the MSISDN is simply to allow a device to be called. A subscriber can have multiple MSISDNs (e.g. one phone number for business, one for personal calls, one for fax, etc.), but generally only one IMSI. The MSISDN does not need to be stored on the SIM card. In cases where it is stored on the SIM, the main reason is so that the user can use check to see what their own MSISDN is (in case they forget). The MSISDN is never signaled to of from the device