Connor-Winfield General Description: The Connor-Winfield Stratum3 Simplified Control Timing Module acts as a complete system clock module for general Stratum 3 timing applications. The STM-S3 is designed with minimum internal control function. Internal control is limited to reversion to Free Run mode upon loss of External Control Inputs. Full external control input allows for selection and monitoring of any of four possible operating states: 1) Holdover, 2) External Clock #1, 3) External Clock #2, and 4) Free Run. The following table illustrates the control signal input and corresponding operational state:
In the absence of External Control Inputs (A,B), the STM-S3 enters the Free Run mode and signals an External Alarm. The STM-S3 will enter other operating modes upon application of a proper control signal. Phase discontinuities are held to stratum 3 levels during transition between operating modes. Mode 1 operation (A=1, B=0) results in an output 16.384 MHz signal that is phase locked to the External Reference Input #1. Mode 2 operation (A=0, B=1) results in an output 16.384 MHz signal that is phase locked to the External Reference Input # 2. Holdover mode operation (A=1, B=1) results in an output signal at or near the 16.384 MHz reference as determined by the latest (last) locked-signal input values and the holdover performance of the STM-S3. Alarm signals are generated at the Alarm Output during Holdover and Free Run operation. Alarm Signals are also generated by a loss-of-lock indication from the PLL and by a Tune-Limit indication from the from the PLL. A Tune-Limit alarm signal indicates that the VCXO tuning voltage is approaching the limits of its lock capability and that the External Reference Input may be erroneous. Real-time indication of the operational mode is available at unique operating mode outputs. Specifications
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