Explanation: Carbon microphones operate by varying the resistance of carbon granules packed between two electrodes. When sound waves strike a diaphragm, it compresses and decompresses these granules. This mechanical action directly modulates a DC current flowing through the microphone, causing significant changes in resistance that produce a relatively **high output voltage** compared to other microphone types like dynamic or condenser mics, which require more amplification. Their direct mechanical sensitivity to sound pressure also makes them quite **sensitive** to acoustic input. Furthermore, the construction of carbon microphones is simple, using readily available and inexpensive materials, resulting in a **low cost** of manufacture. These combined advantages made them prevalent in early radio and telephone systems.