CTCSS stands for Continuous Tone Coded Squelch System, basically it is exactly the same tones that a telephone keypad has when operating menus in an automated system. In order to open a repeater you need the correct tone.
| CTCSS tone letter codes. | ||
|---|---|---|
| Tone A = 67.0Hz | Tone B = 71.9Hz | Tone C = 77.0Hz |
| Tone D = 82.5Hz | Tone E = 88.5Hz | Tone F = 94.8Hz |
| Tone G = 103.5Hz | Tone H = 110.9Hz | Tone J = 118.8Hz |
| (S) special case 100.0Hz GB3FM | ||
| CTCSS by County allocation. | |||
|---|---|---|---|
| County | Tone | Frequency | |
| A | Aberdeenshire | A | 67.0 Hz |
| Angus | F | 94.8 Hz | |
| Anglesey | H | 110.9 Hz | |
| Antrim | H | 110.9 Hz | |
| Argyll and Bute | G | 103.5 Hz | |
| Avon | J | 118.8 Hz | |
| Ayrshire | G | 103.5 Hz | |
| B | Bedfordshire | C | 77.0 Hz |
| Berkshire | J | 118.8 Hz | |
| Border Counties | J | 118.8 Hz | |
| Buckinghamshire | C | 77.0 Hz | |
| C | Cambridgeshire | F | 94.8 Hz |
| Caithness | C | 77.0 Hz | |
| Channel Islands | B | 71.9 Hz | |
| Cheshire | G | 103.5 Hz | |
| Cleveland | J | 118.8 Hz | |
| Clwyd | H | 110.9 Hz | |
| Cornwall | C | 77.0 Hz | |
| Cumbria | C | 77.0 Hz | |
| D | Derbyshire | B | 71.9 Hz |
| Devon | C | 77.0 Hz | |
| Dorset | B | 71.9 Hz | |
| Down | H | 110.9 Hz | |
| Dumfries and Galloway | G | 103.5 Hz | |
| Durham | J | 118.8 Hz | |
| Dyfed | F | 94.8 Hz | |
| E | Essex | H | 110.9 Hz |
| F | Fermanagh | H | 110.9 Hz |
| Fife | F | 94.8 Hz | |
| G | Glamorgan | F | 94.8 Hz |
| Gloucestershire | J | 118.8 Hz | |
| Greater London | D | 82.5 Hz | |
| Greater Manchester | D | 82.5 Hz | |
| Gwent | F | 94.8 Hz | |
| Gwynedd | H | 110.9 Hz | |
| H | Hampshire | B | 71.9 Hz |
| Hereford and Worcester | J | 118.8 Hz | |
| Hertfordshire | D | 82.5 Hz | |
| Highland (West Coast and Islands) | E | 88.5 Hz | |
| Highland (East Coast) | A | 67.0 Hz | |
| Humberside | E | 88.5 Hz | |
| I | Isle of Man | H | 110.9 Hz |
| Isle of Wight | B | 71.9 Hz | |
| K | Kent | G | 103.5 Hz |
| L | Lanarkshire | G | 103.5 Hz |
| Lancashire | D | 82.5 Hz | |
| Leicestershire | C | 77.0 Hz | |
| Lincolnshire | B | 71.9 Hz | |
| London | D | 82.5 Hz | |
| Londonderry | H | 110.9 Hz | |
| Lothians | F | 94.8 Hz | |
| M | Merseyside | D | 82.5 Hz |
| N | Norfolk | F | 94.8 Hz |
| Northamptonshire | C | 77.0 Hz | |
| Northern Isles | C | 77.0 Hz | |
| Northumberland | J | 118.8 Hz | |
| North Yorkshire | J | 118.8 Hz | |
| Nottinghamshire | B | 71.9 Hz | |
| O | Orkney | C | 77.0 Hz |
| Oxfordshire | J | 118.8 Hz | |
| P | Perthshire | F | 94.8 Hz |
| Powys | G | 103.5 Hz | |
| S | Shropshire | G | 103.5 Hz |
| Somerset | C | 77.0 Hz | |
| South Yorkshire | B | 71.9 Hz | |
| Staffordshire North | G | 103.5 Hz | |
| Staffordshire South | A | 67.0 Hz | |
| Suffolk | H | 110.9 Hz | |
| Surrey | D | 82.5 Hz | |
| Sussex (East and West) | E | 88.5 Hz | |
| T | Tyne and Wear | J | 118.8 Hz |
| Tyrone | H | 110.9 Hz | |
| W | Warwickshire | A | 67.0 Hz |
| West Midlands | A | 67.0 Hz | |
| West Yorkshire | D | 82.5 Hz | |
| Wiltshire Northern | J | 118.8 Hz | |
| Wiltshire Southern | B | 71.9 Hz | |
| Worcestershire | J | 118.8 Hz | |