r makes a three-way call, the HLR confirms that the three-way calling feature is available to that user terminal. If there is a normal case for terminating calls, then it is home-system call delivery, where the originating MSC is the serving MSC and there is a single exchange of verifi- cation between the MSC and the HLR. If the termination is a roamer call delivery and the user terminal has an active location, then there is another pair of messages between the HLR and the serving MSC through the serving VLR, as we discussed in the pre- ceding section. If the call delivery involves a border cell, then there is an extra set of five or six messages between the border MSC and the serving MSC to coordinate the page response, to establish the call setup, and to alert the subscriber of an incoming call. Call forwarding can be unconditional (CFU) or conditional. Conditional call forward- ing can be busy (CFB), no answer (CFNA), or default (CFD). CFD forwards calls when either the line is busy or there is no answer. Calls forwarded to the subscriber come through the public switched telephone network (PSTN) and involve no extra signaling. Calls to the user terminal being forwarded someplace else, per subscriber instruction, are another story because they can generate ANSI-41 signaling messages if the user terminal has an active location. When the originating MSC gets the message from the serving MSC that the forwarding condition is met, the originating MSC requests and receives the call-forwarding directory number. Call waiting only generates ANSI-41 signal messages when the call has been handed off to another MSC. The anchor MSC sends the serving MSC a call-waiting message, which is acknowledged. When the subscriber presses the SEND key, the serving MSC de- tects it, signals the flash to the anchor MSC, and awaits acknowledgment of the flash. There are various kinds of subscriber-screened calls. These include calling number identification presentation (CNIP), calling name presentation (CNAP), selective call ac- ceptance 