Abstract ISO/IEC 20114:2004 specifies the signalling protocol for the support of the Make Call Request supplementary service (SS-MCR) at the Q reference point between Private Integrated services Network eXchanges (PINXs) connected together within a Private Integrated Services Network (PISN). Supplementary service MCR enables a Requesting User to request a Co-operating User to establish a new Requested Call to a Destination User. This new Requested Call between the Co-operating and Destination User can be either a Basic call or a Call Independent Signalling Connection. The Q reference point is defined in ISO/IEC 11579-1. Service specifications are produced in three stages and according to the method specified in ETS 300 387. ISO/IEC 20114:2004 contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and stage 2 specifications in ISO/IEC 20113. The signalling protocol for SS-MCR operates on top of the signalling protocol for basic circuit switched call control, as specified in ISO/IEC 11572, and uses certain aspects of the generic procedures for the control of supplementary services specified in ISO/IEC 11582. ISO/IEC 20114:2004 also specifies additional signalling protocol requirements for the support of interactions at the Q reference point between SS-MCR and other supplementary services and ANFs. ISO/IEC 20114:2004 is applicable to PINXs, which can interconnect to form a PISN.