Patent ID: 7411970

Claim:
A method of recovering a clock signal for a TDM output from packets of TDM data which have been transmitted over a packet network, from a source having a source TDM clock to a destination having a destination TDM clock, the method comprising: providing at least some packets with a Remote Timestamp, or information from which a Remote Timestamp can be generated based solely on a bit count determined by counting periods of the source TDM network, and wherein the Remote Timestamp represents the state of the source TDM clock when the packet is created; providing said at least some packets with a Local Timestamp based solely on a bit count determined by counting period of the destination TDM network representing the state of the destination TDM clock when the packet is received; determining a Transit Time value representing the difference between said Local and Remote Timestamps; filtering the Transit Time value over times to produce a filtered Transit Time; and controlling the clock frequency of the TDM output only on the basis of said filtered Transit Time as determined above and independently from the depth of a packet buffer, wherein any transit time greater than a pre-determined value is excluded as an input to any control algorithm for adjusting the clock frequency of said TDM output.