Deep Dive: T2B06
The correct answer is A: DTMF. DTMF (Dual-Tone Multi-Frequency) signaling uses pairs of audio tones to encode numbers, letters, and control functions. Each key on a DTMF keypad generates a unique combination of two tones - one from a low-frequency group and one from a high-frequency group. DTMF is commonly used for repeater control (activating functions, changing settings), autopatch access (connecting to telephone lines), and other control functions. The tone pairs are audible and can be heard when transmitted. Common uses include accessing repeater functions, controlling remote stations, and operating autopatch systems.
Why Other Answers Are Wrong
Option B: Incorrect. CTCSS uses a single continuous sub-audible tone, not pairs of tones. It's for squelch control, not signaling. Option C: Incorrect. GPRS (General Packet Radio Service) is a cellular data service, not an amateur radio signaling method using tone pairs. Option D: Incorrect. D-STAR is a digital voice and data protocol, not a tone-pair signaling system.
Exam Tip
Tone pairs = DTMF. Remember: DTMF uses pairs of audio tones (one low, one high) to encode numbers and control functions. You can hear these tones when transmitted.
Memory Aid
**T**one **P**airs = **D**TMF (think 'TP = DTMF')
Real-World Example
You want to activate a repeater function using DTMF. You press '1' on your radio's DTMF keypad, which generates a tone pair (697 Hz + 1209 Hz). The repeater detects this tone pair and recognizes it as the digit '1', activating the requested function. Each number and letter has its own unique tone pair combination.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T2B
Reference: FCC Part 97.205
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T2B topic.