This Standard specifies the signaling protocol for the support of the Cordless Terminal Location Registration supplementary service (SS-CTLR) at the Q reference point between Private Telecommunication Network (PTNXs) connected together within a Private Telecommunication Network (PTN). SS-CTLR is a supplementary service which enables a CTM user to register at@ or deregister from@ the current location within the PTN. The ability to register at different locations in the PTN at different times enables the CTM user to maintain the provided services (including the ability to make and receive calls) at different access points. Deregistration is used to inform the PTN that the CTM user is temporarily unable to make use of the provided services (including the receipt of calls). Roaming outside the PTN is outside the scope of this edition of this Standard. 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 ENV 41005. This ETS contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and stage 2 specifications in ETS 300 691 and ETS 300 692. The signalling protocol for SS-CTLR operates on top of the signaling protocol for basic circuit switched call control@ as specified in ECMA-143@ and uses certain aspects of the generic procedures for the control of supplementary services specified in ECMA-165. The Standards also specifies additional signalling protocol requirements for the support of interactions at the Q reference point between SS-CTLR and other supplementary services and ANFs. NOTE 1 Additional interactions that have no impact on the signalling protocol at the Q reference point can be found in the relevant stage 1 specifications. This ETS is applicable to PTNXs which can interconnect to form a PTN.