Visitor Location Register (VLR) is a database which stores information about mobile phones that have recently joined a particular area of a mobile operator’s network. It plays a vital role in keeping track of roamed mobile phone subscribers and co-ordinates with the HLR to determine whether the mobile is a permanent subscriber or a temporary one. Whenever a Mobile Switch Center (MSC) detects a new mobile in its network, in addition to creating a new record in the VLR, it also updates the HLR of the mobile subscriber, apprising it of the new location of that mobile (the MSC address). The MSC address received during an HLR lookup for a particular mobile number is useful for identifying numbers roaming in another country. The foreign network that the number is logged onto can also be identified using this data.
