CTCSS & DCS Tone Breakdown

A GMRS.io guide — free GMRS license lookup, repeater directory, and plain-English radio references.

If you've ever tuned to a GMRS channel and heard nothing - even though others say the repeater is active - you're probably missing a CTCSS or DCS tone. These are sub-audible codes that act as a filter on your radio's squelch, so it only opens for transmissions that include the matching tone.

What is CTCSS?

CTCSS (Continuous Tone-Coded Squelch System) sends a low-frequency tone (67.0–254.1 Hz) underneath your voice the entire time you transmit. It's below the normal audible range, so you won't hear it, but other radios detect it. If their CTCSS is set to the same frequency, their squelch opens. If not, they stay silent. There are 50 standard CTCSS tones.

What is DCS?

DCS (Digital-Coded Squelch) works the same way but sends a continuous digital code instead of an analog tone. There are 104 standard DCS codes. DCS is more resistant to false opens from noise or interference than CTCSS. Each code can be normal (N) or inverted (I).

Why they matter

• Repeater access: most GMRS repeaters require a specific CTCSS tone to activate. If you transmit without it, the repeater ignores you
• Channel sharing: multiple groups can use the same frequency with different tones - your radio only unmutes for your group's tone
• Noise filtering: keeps your radio quiet when there's interference or distant stations bleeding in on your channel

Programming tones on your radio

Your radio has two tone settings per channel:

• TX tone (encode): the tone your radio sends when you transmit. Set this to what the repeater or group requires
• RX tone (decode): the tone your radio listens for before opening squelch. Set this to match what the repeater or group sends back

For repeaters, both TX and RX are usually the same tone. Check the repeater listing for the specific tone - on the GMRS.io repeater directory it's listed right alongside each repeater's frequency and offset.

Common GMRS repeater tones

While any tone can be used, these are the most commonly seen on GMRS repeaters:

• 141.3 Hz - very popular default on many repeaters
• 100.0 Hz
• 103.5 Hz
• 110.9 Hz
• 127.3 Hz
• 131.8 Hz
• 156.7 Hz
• 162.2 Hz

CTCSS Brand Cross-Reference Tool

Different radio brands label CTCSS tones by number - for example, Midland "Code 22" = 141.3 Hz. Use the GMRS.io cross-reference tool below to see your radio brand's code-to-frequency mapping, or pick two brands to cross-reference between them.

DCS Brand Cross-Reference Tool

The 104 standard DCS codes are the same across all brands, but menu numbering differs. Some radios let you enter the code directly (e.g. D023), while others use a menu number (e.g. No.1 = D023).

Published by GMRS.io — the free GMRS license lookup and radio guide library. Every guide, a full CTCSS/DCS tone chart, and the GMRS repeater directory live at gmrs.io.