While tones are used to access repeaters, they can also serve purposes for simplex communication as well.
While tones are used to access repeaters, they can also serve purposes for simplex communication as well. In this usage, they’re typically called “privacy tones”. This is a way that allows multiple users to be on the same frequency at one time without hearing one another.
There are different forms of “privacy tones” that can be used:
These systems are not interoperable, but thankfully the CTCSS and PL are, and are what are generally used by repeaters as well as FRS/GMRS radios.
How this works is that each “group” assigns a different tone that they use. Let’s say that there are two groups operating on the same frequency, and one sets a tone of 91.5 and other sets a tone of 127.3. When either group transmits, the other group’s radios don’t receive the correct tone, so they don’t break squelch and output that transmission.
This works well for the intended purpose, but many people incorrectly think that these tones are like “encryption” and make it so no one can hear their transmission. This is incorrect. In the above example, let’s say you are tuned to that frequency with no tone programmed in. You would hear both of the group’s transmissions. As a result, don’t rely on “privacy tones” to provide any privacy.
While CTCSS tones can technically be any frequency between 67 and 254 Hz, “standard” tones have come about. Some radios have additional options, but here are the standard CTCSS tones in use today:
| Standard Tones | Standard Tones | Standard Tones | Standard Tones |
|---|---|---|---|
| 67.0 | 97.4 | 136.5 | 186.2 |
| 71.9 | 100.0 | 141.3 | 192.8 |
| 74.4 | 103.5 | 146.2 | 203.5 |
| 77.0 | 107.2 | 151.4 | 210.7 |
| 79.7 | 110.9 | 156.7 | 218.1 |
| 82.5 | 114.8 | 162.2 | 225.7 |
| 85.4 | 118.8 | 167.9 | 233.6 |
| 88.5 | 123.0 | 173.8 | 241.8 |
| 91.5 | 127.3 | 179.9 | 250.3 |
| 94.8 | 131.8 |
