Avaya Inc.

Avaya Technology LLC

Matthew Duane McShea

Sharmistha Sarkar Das

Peter David Goldman

An apparatus and method is disclosed for synchronizing a timing signal for a computational system to different reference clock signals without impairing the operation of the computational system. A corresponding 'offset' register is provided for each of the reference clock signals (RCS) for storing signal timing differences between the timing signal and RCS. When one of the reference clock signals not used for synchronizing the timing signal, is selected as the signal for synchronizing the timing signal, the corresponding offset register R(for the newly selected reference clock signals) retains its last value prior to the switch, and another register Rstores subsequent signal timing differences between the timing signal and the newly selected reference clock signals. To synchronize the timing signal with the new reference clock signal without distorting the timing signal and impairing the operation of the computation system, differences between Rand Rare output (for successive time intervals) for iteratively adjusting the timing signals. The contents of the offset register Ris incrementally changed toward a predetermined value (i.e., zero) thereby gradually adjusting the timing signals to factor in a potentially large timing change when switching between reference clock signals.

Method and system for switching between two (or more) reference signals for clock synchronization

The present invention is directed to the synchronization of clock frequencies across packet data networks. In particular, one or more communication endpoints may produce a clock signal that is synchronized to a master clock source. Synchronization is performed by providing timing packets containing information regarding a number of clock cycles counted on the master clock source to a controlled clock source. The controlled clock source uses the provided count to increment a counter value. At the same time, the counter value on the controlled clock source is decremented by the controlled clock source clock. The resulting counter value is used to address a correction table. A correction value from the correction table is applied to the frequency control input of the controlled clock source clock.

Method and apparatus for synchronizing clocks on packet-switched networks

A plurality of Goertzel filters whose operating frequencies are distributed across the voice baseband are used to detect voice and control tones in a signal. Filters operating at frequencies of control tones and detecting that most of the signal energy occurs at those frequencies indicates presence of the control tones. At least three of the filters detecting that about 10% to 20% of the signal energy occurs at each of their operating frequencies indicate presence of voice. The total energy detected in the signal being below a noise threshold indicates presence of noise or silence.

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Westminster, CO, United States of America

Matthew Duane McShea