From your description, it sounds as if you desire a network communication "hunt group"-type service; if the first communication server is busy, it will hunt automatically for the next available communication server.
You can do this right now with the Shiva NetSerials. Simply use the Chooser to choose all of NetSerials you wish to have in your "hunt group" and your call will be routed through whichever NetSerial is available. Because the NetSerial is an independent (after initial configuration) network device, you will not need to dedicate a computer to manage it.
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The following Tech Info Library article can help you search for a particular vendor's address and phone number:
Article 17159: "
Locating Vendor Information"