Dual Tone Multi-Frequency refers to the transmission of a selected number or symbol (*) or (#) via the generation of a specific pair of tones when that number's button on a push-button telephone is pressed.

• A. A numeric keypad feature for speed dial.
• B. The transmission of a selected number or symbol (*) or (#) via the generation of a specific pair of tones when that number's button is pressed.
• C. A voice recognition protocol.
• D. A musical telephone feature.

Answer: (B)

Dual Tone Multi-Frequency signaling is the system used by touch-tone phones where pressing a keypad button generates two simultaneous tones from different frequency groups. Each key—digits 0–9 and the symbols * and #—produces a unique pair of tones, so the telephone network can identify exactly which button was pressed. This enables automatic routing, IVR menu navigation, and keypad input for dialing. The description in the option matches this signaling method precisely. The other options describe features not related to how digits or symbols are signaled over the line (speed dial, voice recognition, or a musical feature).