Method to share phone line

1. A method for a first Voice over Internet Protocol (VoIP) device connected to an IP network and a first telephone system to share its telephone resource, comprising:

joining a group of VoIP devices connected to the IP network, the group sharing its telephone resources;

receiving from a caller a telephone number to call a device;

determining a subgroup of the VoIP devices located in the same region as the device;

selecting, from the subgroup of the VoIP devices, a second VoIP device that offers the best performance value less than a threshold, the performance value having an initial value, the performance value being credited each time or each minute that telephone resources of the second VoIP device are shared, the performance score being debited each time or each minute the telephone resources of the group are used by the second VoIP device;

connecting to the second VoIP device over the IP network;

transmitting the telephone number to the second VoIP device, wherein the second VoIP device connects to the device through a second telephone system; and

transmitting to and receiving from the second VoIP device voice signals between the caller and a recipient at the device.

2. The method of claim 1 , wherein:

the first and the second telephone systems are selected from the group consisting of a public switched telephone network (PSTN) and a VoIP telephone system; and

the device is selected from the group consisting of a plain old telephone service (POTS) telephone and a VoIP telephone.

3. The method of claim 1 , wherein said joining a group of VoIP devices comprises:

registering with a master of the group by providing an IP address and at least one of a telephone number and a region of the first VoIP device, the master having a membership list including IP addresses, telephone numbers, and regions of the VoIP devices.

4. The method of claim 3 , wherein the master is selected from the group consisting of one of the VoIP devices and a dedicated server computer.

5. The method of claim 1 , further comprising, prior to said connecting to a second VoIP device:

querying a master of the group for at least one VoIP device located in the same region as the device; and

receiving an IP address of the second VoIP device from the master.

6. The method of claim 3 , wherein the membership list of the VoIP devices further includes performance values for the VoIP devices, the performance values determine if each VoIP device can share its telephone resource and use the telephone resources of the group.

7. The method of claim 6 , wherein the performance value is determined as follows:

P=D−n*U*x+m*S*y,

where “P” is the performance value, “D” is the initial value, “U” is a unit of the telephone resources of the group used by the second VoIP device, “S” is a unit of the telephone resources shared by the second VoIP device, “n” is the number of units U, “x” is a coefficient for U, “m” is the number of units of S, and “y” is a coefficient for S.

8. The method of claim 7 , wherein:

when P>M1, the second VoIP device can use shared resources;

when P>M2, the second VoIP device cannot share its telephone resource;

when P<N1, the second VoIP device cannot use the telephone resources of the group; and

when P<N1, until P>N2, the second VoIP device can share its telephone resources;

“M1,” “M2,” “N1,” “N2” are thresholds and M2>=M1 and N2>=M1>N1.

9. The method of claim 1 , wherein said joining a group of VoIP devices comprises:

registering with one of the VoIP devices to receive a membership list including IP addresses, telephone numbers, and regions of the VoIP devices, wherein each VoIP device stores the membership list.

10. The method of claim 9 , further comprising, prior to said connecting to the second VoIP device:

searching the membership list for at least one VoIP device located in the same region as the device; and

retrieving an IP address of the second VoIP device from the membership list.

11. The method of claim 9 , wherein the membership list of the VoIP devices further includes performance values for the VoIP devices, the performance values determine if each VoIP device can share its telephone resource and use the telephone resources of the group.

12. The method of claim 11 , wherein the performance value is determined as follows:

P=D−n*U*x+m*S*y,

where “P” is the performance value, “D” is the initial value, “U” is a unit of the telephone resources of the group used by the second VoIP device, “S” is a unit of the telephone resources shared by the second VoIP device, “n” is the number of units U, “x” is a coefficient for U, “m” is the number of units of S, and “y” is a coefficient for S.

13. The method of claim 12 , wherein:

when P>M1, the second VoIP device can use shared resources;

when P>M2, the second VoIP device cannot share its telephone resource;

when P<N1, the second VoIP device cannot use the telephone resources of the group; and

when P<N1, until P>N2, the second VoIP device can share its telephone resources;

“M1,” “M2,” “N1,” “N2” are thresholds and M2>=M1 and N2>=M1>N1.

14. The method of claim 1 , wherein said receiving from a caller a telephone number to call a device comprises:

connecting to another device over the IP network; and

receiving a request from the another device to call the device with the telephone number.

15. The method of claim 14 , wherein:

the first and the second telephone systems are each selected from the group consisting of a public switched telephone network (PSTN) and a VoIP telephone system;

the device is one of a plain old telephone service (POTS) telephone and a VoIP telephone; and

the another device is one of a computer and a VoIP telephone.