Gateway MSC, and then used to route the call to the MSC where the called phone is roaming. Locating and ringing the phone When the call arrives at the Visited MSC, the MSRN is used to determine which of the phones in this area is being called, that is the MSRN maps back to the IMSI of the original phone number dialled. The MSC pages all the mobile phone masts in the area that the IMSI is registered in order to inform the phone that there is an incoming call for it. If the subscriber answers, a speech path is created through the Visiting MSC and Gateway MSC back to the network of the person making the call, and a normal telephone call follows. It is also possible that the phone call is not answered. If the subscriber is busy on another call (and call waiting is not being used) the Visited MSC routes the call to a pre-determined Call Forward Busy (CFB) number. Similarly, if the subscriber does not answer the call after a period of time (typically 30 seconds) then the Visited MSC routes the call to a pre-determined Call Forward No Reply (CFNRy) number. Once again, the operator may decide to set this value by default to the voice mail of the mobile so that callers can leave a message. If the subscriber does not respond to the paging request, either due to being out of coverage, or their battery has gone flat/removed, then the Visited MSC routes the call to a pre-determined Call Forward Not Reachable (CFNRc) number. Once again, the operator may decide to set this value by default to the voice mail of the mobile so that callers can leave a message. A roaming user may want to avoid these forwarding services in the visited network as roaming charges will apply. Voice charges In the United States and Canada, callers pay the cost of connecting to the Gateway MSC of the subscriber's phone company, regardless of the actual location of the phone. As mobile numbers are given standard geographic numbers according to the North American Numbering Plan, callers pay the same to reach fixed phones and mobile phones in a given geographic area. Mobile subscribers pay for the connection time (typically using in-plan or prepaid minutes) for both incoming and outgoing calls. For outgoing calls, any long distance charges are billed as if they