Telco

http://www.npac.com/number-portability/how-lnp-works In short: when phone call is made, phone switch checks a database to see if the called number has a secondary phone number (caller LNR), if yes, that number is used to route the call. LNP = Local Number Portability NPAC = Number portability administration center. LNR = Location Routing Number

http://www.npac.com/number-portability/how-lnp-works In short: when phone call is made, phone switch checks a database to see if the called number has a secondary phone number (caller LNR), if yes, that number is used to route the call. LNP = Local Number Portability NPAC = Number portability administration center. LNR = Location Routing Number