| 摘要 |
A digital loss-of-signal ("LOS") detector having a trough circuit and a smearing circuit is described. The trough circuit generates a logic output whenever an incoming communication signal is within a predefined voltage range. The output of the trough circuit is applied to the smearing circuit, which generates an LOS output whenever the output of the trough circuit remains at a predefined logic level for a predetermined length of time. In a second embodiment, a state machine is coupled to the output of the smearing circuit, the trough circuit, and a clock, the state machine generating the LOS indication if the output from the smearing circuit remains at the predetermined logic level for at least a predetermined number of clock cycles.
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