madhuvarsha
2010-07-15, 02:53 AM
ITU-T G.811 PRC ([Only registered and activated users can see links])
This Recommendation outlines the requirements for Primary Reference Clocks (PRCs) suitable for synchronization ([Only registered and activated users can see links]) supply to digital networks ([Only registered and activated users can see links]). These requirements apply under the normal environmental conditions specified for digital equipment.
A typical PRC provides the reference signal for the timing or synchronization of other clocks within a network or section of a network. In particular, the PRC can also provide the reference signal to the slave clock ([Only registered and activated users can see links]) specified in Recommendation G.812 within the network nodes where the PRC is located. This Recommendation defines the PRC output but it does not apply to the output of slave clock directly fed by a PRC. The long-term accuracy of the PRC should be maintained at 1 part in 1011 or better with verification to Coordinated Universal Time ([Only registered and activated users can see links]) (UTC). A PRC may be realized as an autonomous clock, operating independently of other sources. Alternatively, the PRC may be realized as a nonautonomous clock which is disciplined by UTC-derived precision signals received from a radio ([Only registered and activated users can see links]) or satellite ([Only registered and activated users can see links]) system. In either case, the requirements for long-term accuracy and short-term stability, as specified in this Recommendation, apply.
The long-term accuracy of 1 part in 1011 or better is adequate when a single PRC provides the reference synchronization signal to all other clocks within a network (synchronous mode of operation ([Only registered and activated users can see links])). In the pseudo-synchronous mode, i.e. not all clocks in the network have timing traceable to the same PRC, the long-term accuracy is dependent on the number of PRCs in that network.
When more than one PRC is used in a network, a statistical approach is needed to determine the long-term accuracy of each PRC in that network.
This Recommendation outlines the requirements for Primary Reference Clocks (PRCs) suitable for synchronization ([Only registered and activated users can see links]) supply to digital networks ([Only registered and activated users can see links]). These requirements apply under the normal environmental conditions specified for digital equipment.
A typical PRC provides the reference signal for the timing or synchronization of other clocks within a network or section of a network. In particular, the PRC can also provide the reference signal to the slave clock ([Only registered and activated users can see links]) specified in Recommendation G.812 within the network nodes where the PRC is located. This Recommendation defines the PRC output but it does not apply to the output of slave clock directly fed by a PRC. The long-term accuracy of the PRC should be maintained at 1 part in 1011 or better with verification to Coordinated Universal Time ([Only registered and activated users can see links]) (UTC). A PRC may be realized as an autonomous clock, operating independently of other sources. Alternatively, the PRC may be realized as a nonautonomous clock which is disciplined by UTC-derived precision signals received from a radio ([Only registered and activated users can see links]) or satellite ([Only registered and activated users can see links]) system. In either case, the requirements for long-term accuracy and short-term stability, as specified in this Recommendation, apply.
The long-term accuracy of 1 part in 1011 or better is adequate when a single PRC provides the reference synchronization signal to all other clocks within a network (synchronous mode of operation ([Only registered and activated users can see links])). In the pseudo-synchronous mode, i.e. not all clocks in the network have timing traceable to the same PRC, the long-term accuracy is dependent on the number of PRCs in that network.
When more than one PRC is used in a network, a statistical approach is needed to determine the long-term accuracy of each PRC in that network.