A continuous ring such as the one you have described is most often the result of a short somewhere in the system. The fact that the issue continues even when the door station is disconnected from the controller is a good indication the station itself and the wiring from the station are not the cause. If no other components were changed (i.e. phone service, telephones, wiring) often times the issue was a direct result of an excess of voltage hitting the P-0920 over the power line, or potentially the intercom terminal. Lightning is a common culprit especially in mid western states. Lightning can hit the door station, riding the wiring back to the intercom terminal and surge into the unit. The only way to confirm the issue would be to get the unit in for assessment by a Channel Vision Technician. You can contact Channel Vision directly to obtain an RMA for a warranty repair/replace. Please note electrical surges, misuse, and acts of god are not covered under the warranty.