Modem interfers with incoming calls

Whenever the computer is turned on and we receive an incoming phone call the following occurs: 1. The phone rings twice 2. If we do not answer BEFORE the 2nd ring, the caller hears a noise like an incoming fax. 3. If we answer before the end of the second ring, we hear the caller's voice but also hear a noise like an incoming fax.

This problem does not happen if we are on line as we have only one phone line. We do NOT have call waiting. We have uninstalled and unplugged the printer, copier,scanner, fax machine. It still happens. We have become desperate talking to your phone service --Please help us!