CTCSS and DCS tones: the full tone list, explained
By IU4VRB — Licensed Italian radio amateur and the developer of HamQRG. Updated October 5, 2026.
A repeater has to decide, several times a minute, whether the signal on its input is a licensed operator or noise from a passing van. The oldest and still the most common answer is a tone your radio sends underneath your voice, too low to hear.
CTCSS
CTCSS — Continuous Tone-Coded Squelch System, and "PL" on Motorola equipment — is a single tone between 67.0 and 254.1 Hz, transmitted continuously alongside your audio. The repeater opens only when it hears the tone it expects. Everything else is ignored.
The tone is not a password and offers no security whatsoever: the standard set is publicly listed, and every radio can send any of them. It exists to stop a repeater keying up on interference, not to keep anyone out.
DCS
DCS — Digital-Coded Squelch — does the same job with a slow digital code instead of a tone, written as a three-digit octal number such as 023 or 754. It is more resistant to false triggering than CTCSS and less common on amateur repeaters, though some regions use it widely.
Why transmit and receive tones can differ
Some repeaters send a tone on their own output as well as requiring one on the input, so a receiver can be set to stay silent unless the repeater itself is talking. Where the two tones are not the same, a directory has to record both, and a radio programmed with only one may hear nothing at all.
This is common in North America and rare in Europe. It is also a frequent cause of a repeater that appears to be dead: the radio is muting a signal that is perfectly present.
What to set on your radio
| Radio setting | What it does |
|---|---|
| Tone / T | Sends the tone, ignores tones on receive |
| TSQL / T-SQL | Sends the tone and stays muted unless it hears one |
| DTCS / DCS | The digital equivalent of the above |
| Off | Sends nothing — most repeaters will not open |
Plain "Tone" is the right setting most of the time. Use TSQL only when you know the repeater sends a tone back, or you will sit in silence.
The standard CTCSS tone list
There are fifty standard CTCSS tones, from 67.0 Hz to 254.1 Hz. Every modern amateur radio can generate all of them, usually in this order, so the position of a tone in your radio's menu tends to match the table below. Some radios add a few non-standard tones to the list; the fifty here are the ones repeaters actually use.
| 1–10 | 11–20 | 21–30 | 31–40 | 41–50 |
|---|---|---|---|---|
| 67.0 | 94.8 | 131.8 | 171.3 | 203.5 |
| 69.3 | 97.4 | 136.5 | 173.8 | 206.5 |
| 71.9 | 100.0 | 141.3 | 177.3 | 210.7 |
| 74.4 | 103.5 | 146.2 | 179.9 | 218.1 |
| 77.0 | 107.2 | 151.4 | 183.5 | 225.7 |
| 79.7 | 110.9 | 156.7 | 186.2 | 229.1 |
| 82.5 | 114.8 | 159.8 | 189.9 | 233.6 |
| 85.4 | 118.8 | 162.2 | 192.8 | 241.8 |
| 88.5 | 123.0 | 165.5 | 196.6 | 250.3 |
| 91.5 | 127.3 | 167.9 | 199.5 | 254.1 |
Tones close together, such as 67.0 and 69.3 Hz, are easy for a radio to confuse when the signal is weak. That is why neighbouring repeaters are normally given tones well apart, and why a repeater that only opens when you are close may simply be hearing your tone badly rather than not at all.
CTCSS vs DCS: the difference
| CTCSS | DCS | |
|---|---|---|
| Signal | A continuous sine tone | A repeating 23-bit digital word at 134.4 bit/s |
| Written as | A frequency: 88.5, 123.0 | A three-digit octal code: 023, 754 |
| Choices | 50 standard tones | About a hundred standard codes |
| Polarity | Not applicable | Normal or inverted — both ends must match |
| On amateur repeaters | The norm worldwide | Less common, regional |
For a repeater user the difference is only which of the two to set. If a directory gives a number with a decimal point, it is a CTCSS tone; if it gives three digits with no decimal point, often with N or I after it, it is a DCS code and its polarity.
The 1750 Hz tone burst
Before continuous tones were common, European repeaters were opened with a short burst of 1750 Hz at the start of a transmission, and some in IARU Region 1 still are. The burst is audible and is sent once, not underneath your voice. Many radios sold in Europe have a dedicated key or a menu entry for it. If a repeater lists no CTCSS tone and stays closed, a tone burst is worth trying.
Repeater will not open: a checklist
- Check the tone mode is Tone, not Off and not TSQL.
- Check the tone value, digit by digit: 88.5 and 85.4 sit next to each other in most menus.
- Check the shift direction and size against the repeater, and that the shift is switched on.
- If the repeater uses DCS, check the polarity.
- If you can hear the repeater but it hears nothing from you, move: a repeater is line-of-sight, and a few metres of height often fix what power does not.
- If you hear nothing at all, set the receive side to carrier squelch so you can tell a silent repeater from a muted radio.