All About CTCSS and DCSS codes

Carrier Tone Code Squelch System (CTCSS) and Digital Code Squelch System (DCSS) are two mechanisms that radio users frequently use to reduce interference. Some call these "Privacy Codes" or "sub-channels", but they really are not, if you set a radio to recieve without the CTCSS/DCS code, it will receive EVERYTHING on that frequency/channel regardless of the CTCSS/DCS code being transmitted. Many argue that in an emergency scenario, or any time you are using radios from multiple vendors, it is best to NOT use CTCSS/DCS codes as they can be different between vendors. Personally, I still use them and just make sure that the actual values match (Hz not number). 

CTCSS and DCS are mechanisms to "squelch", or ignore an incoming signal unless it contains a matching tone (CCTCSS) or digital code (DCS). A receiver with just a carrier or noise squelch does not suppress any sufficiently strong signal; in CTCSS mode it unmutes only when the signal also carries the correct sub-audible audio tone. The tones are not actually below the range of human hearing, but are poorly reproduced by most communications-grade speakers and in any event are usually filtered out before being sent to the speaker or headphone. 

The Digital-Coded Squelch (DCS) system was developed by Motorola under the trademarked name Digital Private Line (DPL). General Electric in turn started using the same technology under the name of Digital Channel Guard (DCG). The official generic name is CDCSS (Continuous Digital-Coded Squelch System), but most commonly is referred to as DCS. 

 note: many "advanced" radios do NOT refer to these using the "common numbers" but require setting them by the actual frequency (CTCSS) or Value (DCS).

 Here is a table showing the 50 most common CTCSS code values mapped to their frequency (Hz) and the differences between various radios: 

Cobra, Midland, Motorola, Uniden, Backcountry Access, and newerRocky Talkie versions (after 2020) all use the "common" CTCSS values through 38, at 39 and many start using DCS values.  

CTCSS VALUES TABLE
Frequency (Hz)	COMMON	CHEROKEE 465	MOTOROLA SPORT	RADIO SHACK	RETEVIS RB15	Private Line (PL) - Motorola	Notes
150	NATO
67	1	1		1	1	XZ
69.3		2		2 (69.4)		WZ	Some radios use 69.4 Hz instead, which better fits the harmonic sequence, and this tone is often omitted as a choice.
71.9	2	3		3	3	XA
74.4	3	4		4	4	WA
77	4	5	A	5		XB
79.7	5	6		6		WB	Also known by the code SP.
82.5	6	7		7		YZ
85.4	7	8		8		YA
88.5	8	9	B	9		YB
91.5	9	10		10		ZZ
94.8	10	11		11	11	ZA
97.4	11	12	C	12		ZB	Not actually in this harmonic sequence, but an average of the ZA and 1Z tones used to fill the gap between the lower and middle sequences. 98.1 Hz would be the tone after ZA, and the tone before 1Z would be 96.6 Hz, assuming the same harmonics were used.
100	12	13		13		1Z
103.5	13	14		14		1A
107.2	14	15	D	15		1B
110.9	15	16		16		2Z
114.8	16	17		17		2A
118.8	17	18	E	18		2B
123	18	19		19		3Z
127.3	19	20	F	20		3A
131.8	20	21		21		3B
136.5	21	22	G	22		4Z
141.3	22	23		23		4A
146.2	23	24		24		4B
151.4	24	25		25		5Z
156.7	25	26		26	26	5A
159.8		27		27
162.2	26	28		28	28	5B
165.5				29
167.9	27	29		30	30	6Z
171.3				31
173.8	28	30		32	32	6A
177.3				33
177.8
179.9	29	31		34	34	6B
183.5		32		35
186.2	30	33		36	36	7Z
189.9		34		37
192.8	31	35		38	38	7A
196.6		36
199.5		37
203.5	32	38			41	M1
206.5		39
210.7	33	40			43	M2
218.1	34	41			44	M3
225.7	35	42			45	M4
229.1		43
233.6	36	44			47	M5
241.8	37	45			48	M6
250.3	38	46			49	M7
159.8
165.5
171.3
177.3
183.5
189.9
196.6
199.5
206.5						8Z
229.1						9Z
254.1		47				0Z