We actually have two POTS phone lines. One is strictly for the fax machine in the office, the other is the regular house phone line. The fax machine is connected to a battery backup, so I can call out from that as long as the line and the battery backup are working. Otherwise, we have two corded phones (kitchen and bed room) and four cordless phones. I also have an old rotary dial phone that I saved. Not sure why, but you never know.