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What type of repeater signaling uses two audio tones at the same time?

DTMF, the touch-tone keypad sounds.

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  1. DTMF ✔
  2. CTCSS
  3. D-STAR

Why: DTMF means dual-tone multi-frequency. Each keypad button sends two tones at once, just like a telephone keypad.

Huh, didn't know that: DTMF tones are how you reach Internet Radio Linking Project (IRLP) nodes over the air.

The dad joke
Why did the ham dial so happily? Every button had two tones of fun.
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References

Answer: DTMF. DTMF means dual-tone multi-frequency. Each keypad button sends two tones at once, just like a telephone keypad.

  1. HamStudy 2026-2030 Technician pool, section T2B hamstudy.org/browse/E2_2026/T2B
    Dual-Tone Multi-Frequency (DTMF) signaling sends each key press as two simultaneous audio tones
    Checked 2026-10-12.

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