Identifies a reason for redirecting an incoming call. The reason code
 can take one of the following values:

 BUSY             The original DTE was busy and could no accept any
                  more calls.

 OUT OF ORDER     The original DTE was out of order.

 SYSTEMATIC       All calls to the original DTE are automatically
                  rerouted.

 The reason code is used to select a destination for  a redirected
 call. By default, no reason is used.