B expected to be higher performance than that of ePRTC-A, although the values for its performance have not yet been agreed. This recommendation includes the following main topics and annex: Constant time offset compared to the reference time (say, UTC) when locked. Phase error (wander and jitter) produced at the output of the device, which is specified (for wander) as MTIE and TDEV masks. Transient response and phase/time holdover performance, based on the local frequency refer- ence (atomic clock) during loss of phase/time input (from GNSS). Phase and time as well as frequency interfaces, defining the characteristics of the interfaces used to carry physical timing signals. There are performance requirements on the V.11 1PPS in- terface to deliver higher accuracy. Annex A, "ePRTC autonomous primary reference clock requirements." As is the case with the PRTC, if you are interested in the ePRTC, you may also find very helpful the technical report on GNSS systems, "GSTR-GNSS Considerations on the use of GNSS as a primary time reference in telecommunications." It is covered later in the "Other Documents" section, along with a link for its location. Link to recommendation: https://handle.itu.int/11.1002/1000/14014 G.8273.1: Timing Characteristics of Telecom Grandmaster Clocks for Time Synchronization (T-GM) ITU-T G.8273.1 outlines the timing characteristics for the T-GM clocks. From the scope: This Recommendation defines the minimum requirements for the timing functions of the telecom grandmaster clocks that operate in the network architecture as defined in [ITU-T G.8275] and the related profiles defined in [ITU-T G.8275.1] and [ITU-T G.8275.2] Note that this recommendation is still being developed and is not yet published, SO it is not yet available for public download. There are aspects of this document that are covered in other recommendations. G.8273.2: Timing Characteristics of Telecom Boundary Clocks and Telecom Time Slave Clocks for Use with Full Timing Support from the Network ITU-T G.8273.2 is one of the most