AR28-09B router FXS attaches one common phone. Hook off the phone there is busy tone and it cannot dial.
Cancel the configuration of private ringing under subscriber-line view and the service is normal.
The interface configures private-line under subscriber-line view, but configured private number does not exist. After off-hook the system auto dials the number, but it cannot be called. There is busy tone.
It seldom occurs. Check device configuration.