Handling Session timeout for mx.rpx.events.FaultEvent

Hello

   I am new to DataServices. In a Flex Application we are using DataServices to interact with the back end server. In the flex Application I have the following error handler to handle exceptions thrown by Remote Objects

public function faultHandler(event:FaultEvent):void
        {
          
          
        }

In this  I need to determine if  handle if the FaultEvent, was due to a Session Timeout, All other Fault Events are handled in a different way.

Is there any error code/ status code , which I can use to see if the session has timed out in the Front end , Action Script code?

Any help/ pointers are appreciated.

thanks

- Ani