Question T2B06
From subelement T2 - T2B
What type of signaling uses pairs of audio tones?
Why is this correct?
DTMF (Dual-Tone Multi-Frequency) is correct because it literally uses pairs of audio tones for signaling. Each keypad button on your radio generates two simultaneous frequencies, which is why it's called 'dual-tone.' CTCSS uses single sub-audible tones for repeater access, not pairs. GPRS is cellular data technology unrelated to amateur radio audio signaling. D-STAR is a digital voice mode that doesn't use audio tone pairs for signaling.
Memory tip
Remember the name tells the story: 'Dual-Tone Multi-Frequency' directly describes pairs of tones. When you see signaling questions, focus on what the acronym literally means rather than memorizing arbitrary associations.
Learn more
DTMF originated from touch-tone telephone technology and serves a different purpose than repeater access tones. While CTCSS and DCS control repeater squelch for basic access, DTMF sends commands to repeater controllers for advanced functions like autopatch, linking systems, or remote control operations. Modern applications include IRLP node connections and EchoLink access. Understanding this distinction helps you recognize when each signaling method applies in practical amateur radio operation.
Think about it
Why do you think DTMF uses two simultaneous tones instead of just one tone like CTCSS?