Recommendation ITU-T G.8272/Y.1367 specifies the requirements for primary reference time clocks (PRTCs) suitable for time, phase and frequency synchronization in packet networks. It defines the error allowed at the time output of the PRTC. These requirements apply under the normal environmental conditions specified for the equipment. Amendment 1 to Recommendation ITU-T G.8272 (11/2018) provides the following updates: -Modified the scope. -In clause 6, amend the final sentence (immediately before clause 6.1) to read (insertions highlighted): -In clause 6.2, new sentence is added. -Replace the second paragraph after Figure I.4 of clause I.3.1.