ePRC (enhanced Precision Reference clock)
ITU-T G.811.1 outlines the requirements for enhanced primary reference clocks (ePRCs) suitable for frequency synchronization. These requirements apply under normal environmental conditions specified for the equipment.
The ePRC provides the reference signal for the timing or synchronization of other clocks within a network or section of a network. In particular, the ePRC in its autonomous form can provide a frequency input to an enhanced primary reference time clock (ePRTC). This Recommendation defines the ePRC output, but it does not apply to the output of a slave clock directly fed by an ePRC. The long-term accuracy of the ePRC should be maintained at 1 part in 10^12 or better, with verification to coordinated universal time (UTC). An ePRC may be realized as an autonomous clock, operating independently of other sources. Alternatively, the ePRC may be realized as a non-autonomous clock which is disciplined by UTC-derived precision signals received from a radio or satellite system. In either case, the requirements for long-term accuracy and short-term stability, as specified in this Recommendation, apply.