A system is provided for detecting a fault in a signal transmission path. In one embodiment, the system can include a variable amplitude signal attenuator which is operable to modify an input signal by variably attenuating a signal voltage swing of the input signal. Desirably, the input signal is attenuated only when transitioning from a high signal voltage level towards a low signal voltage level d variably, such that a larger high-to-low signal voltage swing is attenuated more than a smaller high-to-low signal voltage swing. Desirably, a comparator, which may apply hysteresis to the output signals, may detect a crossing of a reference voltage level by the modified input signal. In this way, when the comparator does not detect an expected crossing of the reference voltage level by the modified input signal, a determination can be made that a fault exists in the signal transmission path.