There is a feature called Delayed Ring Transfer (DRT). When an external incoming call isn't answered after a given number of rings, that call also starts ringing the prime set.
DRT is a system feature: it isn't invoked by a feature code, but rather configured in programming. If that is what you are looking for, you would have to make a few changes to the existing programming.
First, you need to turn on DRT:
System Programming > Feature Settings > DRT to Prime: Y
System Programming > Feature Settings > DRT Delay: [Number of rings]
Second, you need to assign a prime set to each line (and target line):
Lines > [Line] > Trunk/Line Data > Prime Set: [DN]
Before you assign a (or change the existing) prime set, you must be aware that some other calls will end up at the prime set. Here are a few scenarios:
[ul]
[li]If a line doesn't ring any set at all, the line will ring the prime set.[/li]
[li]If a line usually rings a set, but that set has Do Not Disturb (DND) turned on, the line will ring the prime set instead.[/li]
[li]If a line usually rings a set, but that set doesn't have any free button to receive the call, the line will ring the prime set instead.[/li]
[li]If a camp, park or transfer callback isn't picked up, it will come to the prime set.[/li]
[li]If a held call isn't picked up after a few minutes, it will beep the prime set.[/li]
[/ul]
Depending on what you need, there might be other features better suited. For example, Call Forward No Answer can also delay ringing. If you can tell us when you want that M7310 to ring and when you don't want it to ring, it will help to point you in the right direction.
