This Recommendation specifies the stage 3 of the diversion supplementary services for the Integrated Services Digital Network (ISDN) as provided by public telecommunications operators at the T reference point or coincident S and T reference point (as defined in Recommendation 1.411 [I]) by means of the Digital Subscriber Signalling System No.1 (DSS 1). Stage 3 identifies the protocol procedures and switching functions needed to support a telecommunications service (see Recommendation I.130 [2]).