Patent ID: 7542483
Filing Date: 2009-06-02
Classification: H03L,H04J

Abstract:
1. A method for operating a line-card having a transponder and a transceiver for an asynchronous data transmission standard to relay data in accordance with a synchronous data transmission standard, said method comprising: receiving a remotely transmitted signal formatted in accordance with said synchronous data transmission standard by said transponder; recovering a clock signal from said remotely transmitted signal by said transponder; in a first mode, directing said recovered clock signal to a clock input of said transceiver; in a second mode, directing a locally generated clock to said clock input of said transceiver; switching from said first mode to said second mode upon loss of said remotely transmitted signal or upon loss of recovered framing in said remotely transmitted signal; during said first mode, filtering said clock input using a phase lock loop operating at a first (fast) time constant; and when switching from said second mode to said first mode, filtering said clock input using said phase lock loop operating at a second time constant, said second time constant being shorter than said first time constant.