Symmetricom 1000, 1100 manual Selecting the Input, Input State, Revertive Switching

Chapter 1 Overview of the TimeProvider

Reference Input Signals

Make the input connections using the procedures described in Making Input Connections, on page 63, then provision the inputs using the software commands described in Provisioning the Input Reference, on page 108.

Input State

You can provision each input to one of three states:

Disabled – the input is not used

Monitor – the system monitors the input for signal faults and performance data, but it cannot be selected as the system reference

Enabled – the system monitors the input for signal faults and performance data. The input can be selected as the system reference in SSU or SUB mode or as a backup reference in PRR mode.

Selecting the Input

Many considerations influence which system reference you choose:

SSM or User-assigned Quality Level

User-assigned Priority Level

Switching mode

User-assigned Input State

Active alarms on an input

You can provision the TimeProvider to automatically select the highest-quality input based on priority and performance qualification, or you can manually select the input signal you want to use. If that signal becomes disqualified for any reason, the local oscillator goes into the Holdover mode.

Revertive Switching

Telcordia GR-378 and GR-1244 define two reference selection modes: Revertive and Non-revertive. In the revertive mode, when an input used as the system reference is disqualified (for any reason), if that input returns, it reverts to the system reference when the disqualifying reason is removed. The system reference switches two times: once when the disqualifying event occurs, and again when the input is no longer disqualified. In the non-revertive mode, the system reference does not revert to the initial input when the reason for disqualification is removed. The system reference switches only once when the disqualifying event occurs.

Quality Level and Priority Level

When the REFMODE parameter is provisioned to AUTO, the system reference switches when the input signal is disqualified. When the input signal is re-qualified, the TimeProvider can either keep the current reference or switch back to the re-qualified signal. When the REFMODE parameter is set to FORCED, then the reference does not switch and remains locked to that reference and the local oscillator enters Holdover mode if the input is not re-qualified. You may also

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