Patent ID: 6980568

Claim:
A network switch comprising: a clock input/output (I/O) card having a first input; a first clock unit coupled to the clock I/O card, wherein the first clock unit comprises: a first relay coupled to the first input of the clock I/O card; a first termination module coupled to the first relay; a first framer coupled to the first termination module; and a first multiplexer coupled to the first framer; and a second clock unit coupled to the clock I/O card, wherein the second clock unit comprises: a second relay coupled to the first input of the clock I/O card; a second termination module coupled to the second relay; a second framer coupled to the second termination module; and a second multiplexer coupled to the first framer and the second framer, wherein clock references signals from the first input are received from the first framer whenever the second clock unit is operating in a backup mode, wherein the first clock unit further comprises a first timing unit coupled to the first multiplexer and the second clock unit further comprises a second timing unit coupled to the second multiplexer, wherein the second multiplexer selects the input clock reference signals received from the first framer whenever the second clock unit is in the backup mode.