The Local System reference is a "Self" reference, i.e. NetClock uses itself as an input reference for Time, or as a 1PPS reference. The Local System is a unique input reference in that it can be used as either the Time reference, or the 1PPS reference, but never both.
Note: For NetClock to operate as a Local System reference, you must have either a valid external Time reference, or a valid external 1PPS reference.
- When the Time reference is configured as Local System, NetClock's System Time is considered a valid reference, as long as the external 1PPS input reference is valid.
- Vice versa, when the 1PPS reference is configured as Local System, NetClock's built-in oscillator is considered a valid reference, as long as the external Time reference is valid.
Use case "Local System Time"
The Local System reference when used for Time allows NetClock to operate using its current Time-of-Day (ToD) for Time, while synchronized to an external 1PPS reference.
While you may intentionally offset the time in this scenario, the second will be precisely aligned to the external 1PPS reference. Therefore, this use case qualifies as a legitimate, traceable time source.
Instead of an offset time, Local System can also be used as a backup Time reference (e.g., Priority "2"): Should the external Time reference become invalid, the Local System Time will become the valid backup reference, disciplined by the external 1PPS reference: NetClock will transition to the Local System Time, without going into Holdover.
Use case "Local System 1PPS"
The Local System reference can also be used for 1PPS: This allows NetClock to operate using an external ToD for time, while generating 1PPS from its own internal oscillator.
In this rare use case the 1PPS is NOT aligned to any standard, therefore the time may drift, and must be considered untraceable.