Worsening static and now completely dead. The phones test OK on the
network interface device box attached to the exterior siding of the
house, which suggests that the problem is inside the house. We have a
maintainance policy for inside the house. Could this problem be due
to mice chewing wires? If so is there a danger? -- Worried

You can easily determine if it is a short or an open circuit with a
multi-meter. Remove all phones and detach the house phone wiring from the
network inferface device. Now measure the resistance across the two middle
contacts (red/green wires) of any phone jack. If the resistance is close to
zero then you have a short.

If there is indeed a short, it would be interesting to see how the telco
technician locate and fix it -- there is no simple tool to locate short
circuit.