This Recommendation specifies the requirements for enhanced primary reference time clocks (ePRTCs) suitable for time@ phase and frequency synchronization in packet networks. These requirements apply under the normal environmental conditions specified for the equipment. The ePRTC provides a reference time signal traceable to a recognized time standard (e.g.@ coordinated universal time (UTC)) and also a frequency reference. Compared to the primary reference time clock (PRTC) as defined in [ITU-T G.8272]@ the ePRTC is subject to more stringent output performance requirements and includes a frequency input directly from an autonomous primary reference clock. The performance of the autonomous primary reference clock for this particular application is specified in Annex A. An ePRTC provides the reference signal for time@ phase@ and frequency synchronization for clocks within a network or section of a network. In particular@ the ePRTC can also provide the reference signal to the telecom grand master (T-GM) within the network node where the ePRTC is located. This Recommendation defines the ePRTC output requirements. The requirements for the ePRTC integrated with a T-GM clock are for further study.