This may indicate that the phone is not reregistering on its set interval with the ThinkTel switch (3600s). The switch will assume that the device is no longer present and will drop any calls that may be in progress.
- Verify the latest firmware is being run on the phone/adapter.
- If you are running your phone behind a NAT firewall that is SIP aware, packet mangling may be occuring.
- If you have other IP handsets or ATAs, check if they are also configured with the same phone number. This could create registration conflicts and sudden call drops while the other devices register on the same number.