What is the typical failure mode for a carbon microphone in these sets?

• A. Carbon microphone degradation and reduced sensitivity due to wear or moisture.
• B. Constant overheating.
• C. Automatic shutdown.
• D. Increased microphone sensitivity.

Answer: (A)

The typical failure mode is degradation of the carbon microphone and reduced sensitivity from wear or moisture. In these sets, sound is converted to electrical signal as the diaphragm moves and compresses carbon granules between contacts; the changing resistance creates the audio signal. Over time, repeated use and exposure to moisture cause the granules to wear, clump, or shift contact, so the resistance change for a given sound becomes smaller. That means a voice comes out weaker or muffled, even if you speak clearly and press the switch normally.

Moisture from sweat, humidity, or condensation accelerates this wear, further decreasing performance. This is why carbon microphones tend to lose sensitivity with age and exposure rather than improve. Other options—constant overheating, automatic shutdown, or increased sensitivity—don’t fit how carbon microphones operate in these sets, since they are passive devices whose main issue is loss of signal due to mechanical and moisture-related wear rather than thermal or automatic control failures.