Question
What term describes the use of a sub-audible tone transmitted along with normal voice audio to open the squelch of a receiver?
Answer Options
- A) Carrier squelch
- B) Tone burst
- C) DTMF
- D) CTCSS
Correct Answer: D
Explanation
The system described is CTCSS, which stands for Continuous Tone-Coded Squelch System (also known by the trade name Tone Squelch or PL tone). It involves transmitting a continuous, very low-frequency (sub-audible) tone along with the voice audio. This tone is below the human hearing range, so you don’t hear it during a normal conversation.
A repeater’s receiver can be configured to only activate its transmitter when it detects a signal carrying the correct CTCSS tone. This keeps the repeater silent and prevents it from activating for unwanted signals, noise, or signals from distant repeaters sharing the same frequency.
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