Convert landline telephone call and transmit over network?

I wish to convert an incomming call on one computer on my network and answer it on a second computer in the same network. The incomming call on the first computer will be received by a standard 56k internal modem. The software I'm looking for should be able to transmit this call over the network to the second computer so that a user can answer it there (not with a standard phone line, perhaps a headset or bluetooth wireless headset) Any ideas on this setup?

Thanks guys for the answer, but as to the VOIP gateway, will I need to purchase additional hardware or can software on that computer simply use the internal modem to accept the analog signal and convert to IP for use on the network? I doubt I'll have latency issues or bandwidth problems in the network as it's a simple setup with not more than 4 pc's on the network (only 2 will be involved)

I believe you can achieve what you want but not the way you want to do so.

The analog inbound call from the Public Switched Telephone Network (PSTN) needs to be converted to work on your LAN. Your LAN uses TCP / IP protocol.

Voice over Internet Protocol (VoIP) is designed to transmit the traditional voice over IP.

Most people incorrectly consider VoIP to be the so called "low cost" carriers that use your broadband connection for voice transport. It is a lot more than that and those low cost carriers in fact do not have the ability to provide quality voice transport over the internet.

Typically here is what you would do (in a nutshell):

1. The PSTN (analog in your case) signal is fed into a VoIP gateway which converts the Voice into IP packets and assigns these packets priority over data packets in your LAN. This priority assignment is critical if you wish to have good quality voice; similarly network hardware must be able to also respect and process priority marked packets or voice quality will be unpredictible (sometimes good, sometimes bad). There may be pc based software that can convert analog voice into IP packets but I don't know if it can use your existing modem; there may also be a pci card that you can insert into your pc to do this but I have not researched this.
2. Your LAN must have switches which respect and properly process prioity packets over non-priority packets. If your switches, routers (if applicable), etc cannot respect and process priority packets properly, see if a firmware upgrade will do so and do the firmware upgrade. If firmware upgrade will not do this, replace the network hardware with devices that will.
3. Your IP packet voice is now handled via IP telephony. This can be done via IP phones that plug into the network and / or IP phone software that can be loaded onto your PC. There are different types of pc based IP software and related headsets of all types and sorts. I suspect there are blue tooth as well.

Now that I have given you an overview, here are critical points:

1. Packet Priority assignment - make sure your voice phone packets are assigned priority over data packets. IP phones and IP gateways should have this capability built in and you should be able to set this and alter this if traffic demands such.
2. Network switches and network routers (if you use them internally) must respect and process priority packets properly. Low cost household network swtiches and routers are not able to do this and if you do not upgrade voice quality will be unpredictible. [Understand that voice packets must complete their travel in approximately 120 milliseconds (packet priority and low latency), must arrive in order (packet order), must arrive at about the same time delay (low jitter).
3. Your network must have sufficient capacity to handle voice and data. A typical IP phone takes 100 kbps to initiate and about 60 Kbps to maintain. For a small network, you should be set up to run at 100 Mbps and should not be so heavily loaded that the average demand before voice is 60 Mbps. Most home networks are no where near this average use.

Remember that a data network can handle irregular demand, packet loss, packet disorder in arrival, and jitter without an issue of substance. Voice cannot so you are adding a level of complexity to the network. It is more engineering to be sure but it can do the job.

Finally, the low cost phone carriers that use the Internet as their transport means are not able to assign and maintain packet priority over the internet. The Internet does not recognize or respect packet priority. This is why these carriers have irregular quality and some people state it works for them (because, unknown to them the traffic happens to be so low at this time that things are working) and others state it worked before but does not now or it works sometimes during the day but not other times (because network traffic is sufficiently high that priority assignment and priority heeding is required but unavailable).

I hope this has helped.

You will need another computer on the network which would run ASTERISK, a soft PBX, with an analog card to connect to the phone lines. You will also need a softphone such as GIZMO installed on the other computers to allow them to become extensions of the ASTERISK PBX. once installed, you could also access the system from anywhere in the world for no charge as long as you can get an internet access

Bob who is both a telecommunications engineer and a programmer