This Amendment 3 to the ISUP Specification Q.764 (12/1999) contains three modifications: 1) Fallback procedures, modification of clause 2.5.2.2.2. 2) Procedures to support the calling party's category for calls from mobile terminals, new procedures in a new clause 2.26. 3) Signalling procedures for automatic re-routing (crankback), new procedures in a new clause 2.27. NOTE - Previous amendments to ITU-T Rec. Q.764 (12/1999) still apply and need to be taken into account when applying this amendment.