What are the symptoms of hum on an upstream digital modulation channel?

The symptoms of hum on an upstream digital modulation channel primarily manifest as bit errors similar to impulse noise. This is because hum can introduce unwanted electrical signals that interfere with the normal modulation process, leading to errors in the transmission of data. These incorrect bits can be likened to the effects of impulse noise, which is characterized by short, sharp disturbances that disrupt the signal. The digital channel struggles to maintain the accuracy of the modulation due to this interference caused by hum.

When hum is present, it often results in unpredictable fluctuations in the signal that cause bits to be read incorrectly, similar to how impulse noise would affect a digital transmission. This can ultimately lead to wide-ranging issues in data integrity, requiring error correction processes and potentially disrupting communication channels.

In contrast, other options present scenarios that are unlikely in the presence of hum. For example, signal loss with no modulation is typically indicative of a complete signal failure rather than the specific interference caused by hum. An increase in bandwidth usage could suggest inefficient transmission but does not directly relate to the interference characteristics of hum. Consistent transmission without interruptions would not be expected as hum creates disturbances that would disrupt the continuity of the signal.