Recommendation ITU-T G.8272.2 specifies requirements for coherent network primary reference time clocks suitable for time, phase and frequency synchronization in networks. These requirements apply under the normal environmental conditions specified for the equipment. Amendment 1 to Recommendation ITU-T G.8272.2 (2024/01) provides the following updates: Added material to the scope on cnPRTC clocks and cnPRTC groups of clocks. Added material to clause 10 Coherency. Changed “time standard” to “time scale” and clarified the use of UTC. Replaced the term “calibration” with the more appropriate term “compensation”. Added material on “UTC time signal source” to clause 5 Conventions. Added new Appendix IV cnPRTC coherency requirement assumptions (GNSS example)