Managing the Oscillator
The purpose of the built-in oscillator is to provide NetClock with an accurate and very stable internal frequency source. This allows NetClock to go into a holdover mode in the event that external time or frequency references are lost or become invalid. However, the oscillator can also be used as a legitimate 1PPS reference during normal operation, in conjunction with an external time reference (for more information, see Configuring Input Reference Priorities.)
NetClock’s internal oscillator is normally disciplined to an input reference (such as GNSS, IRIG input, 1PPS input, etc.) in order to provide the highest degree of oscillator accuracy and to account for oscillator drift. While disciplining (with a 1PPS input reference input present and valid), the oscillator’s output frequency is monitored and based on the measured frequency, the oscillator is steered to maintain a very accurate 10 MHz output. If no valid 1PPS input references are present (or input references are present but not considered valid), the oscillator will be in Freerun mode instead.
If no external input reference such as GNSS, IRIG, etc. is available (or is temporarily lost), NetClock may become an NTP Stratum 2 or higher reference. If so configured, NetClock can use a reference such as an NTP daemon, or TimeKeeper, referred to as a Host Reference. If the Host Reference becomes active, it will automatically take over the disciplining of the oscillator. This built-in functionality is referred to as Host Disciplining.
Note: Host disciplining is NOT supported by NetClock units that are equipped with a Rubidium oscillator.
The Oscillators Settings page provides the user with some control of the disciplining process. This page is also used to configure the length of time NetClock is allowed to remain in the Holdover mode when all references are lost.