In radio communications, “tone squelch” and “noise squelch” are two methods used to improve the clarity of received signals by filtering out unwanted transmissions and noise.
Here’s how they differ:
Tone Squelch (CTCSS/DCS)
- Function: Tone squelch systems use sub-audible tones (Continuous Tone-Coded Squelch System – CTCSS) or digitally coded squelch (Digital-Coded Squelch – DCS) that are transmitted along with the voice signal. Receivers set to the same tone or code will open the squelch only when this specific tone or code is detected.
- Purpose: The primary purpose is to prevent the receiver from opening up due to transmissions from other users on the same frequency who are not part of the same group.
- Use Cases: Commonly used in busy radio environments like cities where many users might share the same frequency channels.
Noise Squelch
- Function: Noise squelch works by setting a threshold level that the signal must overcome to open the squelch. If the received signal’s strength is lower than this threshold, typically because it’s just noise, the squelch remains closed.
- Purpose: To block out background noise or weak transmissions that do not signify actual communication.
- Use Cases: Useful in any radio environment to clean up reception but particularly effective in less congested or more controlled communication scenarios.
Summary
Both systems are vital for maintaining clear and effective communication channels, especially in environments where radio frequency interference is common. Tone squelch is more selective, while noise squelch is more general in its application.