IMPORTANT TELECOMMUNICATIONS ABBREVIATIONS YOU SHOULD KNOW.

GSM: Global system for mobile communications
PMB: Per munite billing
SIM: Subscribers identification module
DC: Direct current
BAIC: Barring of all incoiming calls
IDD: International direct dialling
PIN: Personal identification number
BI: Basic information
OSS: Operation and support sub-system
HLR: Home location register
SMS: Short message service
ISDN: Integrated service digital network
PC: Personal computer
PUK: PIN unblocking keys
PTC: Private telecommunications center
MRF: Mobile radio frequency
IMEI: International mobile equipment identity
CUG: Close users group
MCC: Mobile country code
CW: Call waiting
PSB: Per seconds billing
MMS: Multimedia message service
WAP: Wireless application protocol