I have a small system setup with 6 cisco SPA 525's. All phones are on the same firmware version 7.4.8. All of the phones were configured first by provisioning from 3cx, then provisioning was removed from the phones and a few settings like line txt labels have been modified manually. I have two of these phones side by side. On one when I go off hook either by picking up the reciever or pressing speaker you get the normal dial tone sound. The other phone when you go off hook you get a odd "stutter" tone of around 10 "beeps" if you will that are the same as the dial tone sound then you get a steady dial tone. You can still dial during this stutter sound but I dont really understand whats causing it. It happens every time on this one phone and I cant seem to find any configuration on that phone that is different.