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CTCSS Tones
 
Continuous Tone-Coded Squelch System or CTCSS is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel like UHF CB and is quite often referred to as tone squelch .
 
Where more than one user group is on the same channel, CTCSS filters out other users if they are using a different CTCSS tone or no CTCSS. Instead of turning on the receive audio for any signal, the two-way radio receiver's audio turns on only in the presence of a signal AND the correct tone.
 
A carrier squelch or noise squelch receiver is unlocked and will let any signal in. A receiver with CTCSS locks out all signals except ones encoded with the correct tone.
 
Following is a list of the common CTCSS Code Numbers and Frequency
 
 
Code Number Frequency (Hz)
Code Number
Frequency (Hz)
oF
 OFF
20
131.8
1 67.0
21
136.5
2 71.9
22
141.3
3 74.4
23
146.2
4 77.0
24
151.4
5 79.7
25
156.7
6 82.5
26
162.2
7 85.4
27
167.9
8 88.5
28
173.8
9 91.5
29
179.9
10 94.8
30
186.2
11 97.4
31
192.8
12 100.0
32
203.5
13 103.5
33
210.7
14 107.2
34
218.1
15 110.9
35
225.7
16 114.8
36
233.6
17 118.8
 37
241.8
18 123.0
38
250.3
19 127.3