Symmetricom 1100, 1000 manual Input/Output and Clock Module IOC

Chapter 1 Overview of the TimeProvider

Functional Description

Integrated Information Management Card with TimeProvider Interface Unit (IMC/TPIU)

For users who use the GPS feature, the integrated IMC/TPIU combines the features of the IMC card with the TPIU into the same size footprint as a stand-alone IMC card (see the descriptions of the IMC and TPIU). The IMC/TPIU reduces rack space requirements by eliminating the rack mounted stand-alone TPIU. Functionally, the IMC/TPIU supports the same functions as the IMC card, controlling all communication channels within the TimeProvider and managing GPS control processes. If the IMC/TPIU fails or is removed, GPS operations cease.

Input/Output and Clock Module (IOC)

The TimeProvider operates with one or two IOCs. A second IOC in the shelf provides protection should the primary IOC fail. The IOC accepts the incoming reference signal and decodes the SSM, if present.

With the system properly provisioned and a reference signal selected, the local oscillator in the IOC operates in one of the following states:

Warm-up – For up to 20 minutes after applying power to the shelf, the IOC operates in warm-up mode.

Fast-lock – After warm-up is complete, the IOC enters the fast-lock state, where it quickly frequency-locks the local oscillator to the reference input.

Normal lock – After the IOC has completed the fast-lock cycle, it enters the normal lock mode, in which the TimeProvider uses the proper amount of filtering for the selected mode. When set to the SSU mode and locked to an active input traceable to a Primary Reference Source (PRS), the TimeProvider complies with the G.811 and GR-2830-CORE standards.

Holdover – If the reference signal is lost, then the clock enters the holdover mode. The accuracy of the TimeProvider output is then dependent on the quality level of the oscillator in the IOC.

Free-run – If the IOC starts without a system reference, the TimeProvider enters the free-run state after warm-up. If a reference is applied, then the TimeProvider enters the fast-lock and then the normal-lock states.

Bridging – In the event that all input references are lost, the TimeProvider goes into the bridging mode where the outputs continue to provide accurate timing outputs for a user-defined amount of time. If the inputs have not been requalified before the bridging time has elapsed, then the TimeProvider enters the holdover mode.

After the IOC has been in the Normal lock mode for at least three days, SmartClock holdover mode becomes available. Compared to the normal holdover mode, this mode provides a superior output quality.

32 TimeProvider User’s Guide 097-58001-02 Revision G – April 2008