PRTC

The primary reference time clock (PRTC) located in core centers provides reference time and phase synchronization signal traceable to a recognized time standard UTC(*) for other clocks within the telecommunication networks. As packet timing requirements emerged, ITU-T developed the primary reference time clock (PRTC) standard to include the requirements for time and phase for transport over a packet network.
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.
This Recommendation defines two types of PRTCs, PRTC-A and PRTC-B. The time output of PRTC-B is more accurate than that of PRTC-A.
Under normal, locked operating conditions, the time output of the PRTC-A, or the combined PRTC-A and T-GM function, should be accurate to within 100 ns or better when verified against the applicable primary time standard (e.g., UTC).
Under normal, locked operating conditions, the time output of the PRTC-B, or the combined PRTC-B and T-GM function, should be accurate to within 40 ns or better when verified against the applicable primary time standard (e.g., UTC).