989:-603-E; the CTCSS tones also may be listed in manufacturers instruction, maintenance or operational manuals. Some systems use non-standard tones. The NATO Military radios use 150.0 Hz, and this can be found in the user manuals for the radios. Some areas do not use certain tones. For example, the tone of 100.0 Hz is avoided in the United Kingdom since this is twice the UK mains power line frequency; an inadequately smoothed power supply may cause unwanted squelch opening (this is true in many other areas that use 50 Hz power). Tones typically come from one of three series as listed below along with the two character PL code used by Motorola to identify tones. The most common set of supported tones is a set of 39 tones including all tones with Motorola PL codes, except for the tones 8Z, 9Z, and 0Z (zero-Z). The lowest series has adjacent tones that are roughly in the harmonic ratio of 2 to 1 (≈1.035265), while the other two series have adjacent tones roughly in the ratio of 10 to 1 (≈1.035142). An example technical description can be found in a Philips technical information sheet about their CTCSS products.
1129:
about 200 milliseconds. In older systems, the tone decoders used mechanical reeds to decode CTCSS tones. When audio at a resonant pitch was fed into the reed, it would resonate, which would turn on the speaker audio. The end-of-transmission phase reversal (called "Reverse Burst" by
Motorola (and trademarked by them) and "Squelch Tail Elimination" or "STE" by GE ) caused the reed to abruptly stop vibrating which would cause the receive audio to instantly mute. Initially, a phase shift of 180 degrees was used, but experience showed that a shift of ±120 to 135 degrees was optimal in halting the mechanical reeds. These systems often have audio muting logic set for CTCSS only. If a transmitter without the phase reversal feature is used, the squelch can remain unmuted for as long as the reed continues to vibrate—up to 1.5 seconds at the end of a transmission as it coasts to a stop (sometimes referred to as the "flywheel effect" or called "freewheeling").
1156:
tone squelch turned off will hear everything on the channel. GMRS/FRS radios offering CTCSS codes typically provide a choice of 38 tones, but the tone number and the tone frequencies used may vary from one manufacturer to another (or even within product lines of one manufacturer) and should not be assumed to be consistent (i.e. "Tone 12" in one set of radios may not be "Tone 12" in another).
38:
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selectable number of milliseconds before it is retransmitted. During this fixed delay period (the amount of which is adjusted during installation, then locked down), the CTCSS decoder has enough time to recognize the right tone. This way the problem with lost syllables at the beginning of a transmission can be overcome without having to use higher frequency tones.
237:, the microphone is usually stored in a hang-up clip or a hang-up box containing a microphone clip. When the user pulls the microphone out of the hang-up clip to make a call, a switch in the clip (box) forces the receiver to revert to conventional carrier squelch mode ("monitor"). Some designs relocate the switch into the body of the microphone itself. In
262:
When that occurs, the system transmitter turns on, encoding the CTCSS tone on its carrier signal (the output frequency). All radios in the system start decoding after they sense a carrier signal then recognize the tone on the carrier as valid. Any distortion on the encoded tone will also affect the decoding time.
177:, and their transmissions interfere with each other; however; the interference is masked under most conditions. Although it provides some protection against interference, CTCSS does not offer any security against interception or jamming, and receivers without CTCSS enabled will still hear all traffic.
1155:
and other consumer-grade radios often include a CTCSS feature called "Interference
Eliminator Codes", "sub-channels", "privacy tones", or "privacy codes". These do not afford privacy or security, but serve only to reduce annoying interference by other users or other noise sources; a receiver with the
1137:
In non-critical uses, CTCSS can also be used to hide the presence of interfering signals such as receiver-produced intermodulation. Receivers with poor specifications—such as scanners or low-cost mobile radios—cannot reject the strong signals present in urban environments. The interference will still
261:
systems, the time lag can be significant. The lower tone may cause one or two syllables to be clipped before the receiver audio is unmuted (is heard). This is because receivers are decoding in a chain. The repeater receiver must first sense the carrier signal on the input, then decode the CTCSS tone.
252:
A CTCSS decoder is based on a very narrow bandpass filter which passes the desired CTCSS tone. The filter's output is amplified and rectified, creating a DC voltage whenever the desired tone is present. The DC voltage is used to turn on, enable, or unmute the receiver's speaker audio stages. When the
269:
In early systems, it was common to avoid the use of adjacent tones. On channels where every available tone is not in use, this is good engineering practice. For example, an ideal would be to avoid using 97.4 Hz and 100.0 Hz on the same channel. The tones are so close that some decoders may
256:
Because period is the inverse of frequency, lower tone frequencies can take longer to decode (depends on the decoder design). Receivers in a system using 67.0 Hz can take noticeably longer to decode than ones using 203.5 Hz, and they can take longer than one decoding 250.3 Hz. In some
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Some professional systems use a phase-reversal of the CTCSS tone at the end of a transmission to eliminate the squelch crash or squelch tail. This is common with
General Electric Mobile Radio and Motorola systems. When the user releases the push-to-talk button the CTCSS tone does a phase shift for
184:
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
265:
Engineered systems often use tones in the 127.3 Hz to 162.2 Hz range to balance fast decoding with keeping the tones out of the audible part of the receive audio. Most amateur radio repeater controller manufacturers offer an audio delay option—this delays the repeated speech audio for a
297:
under the trademarked name
Digital Private Line (DPL). General Electric responded with the same system under the name of Digital Channel Guard (DCG). The generic name is CDCSS (Continuous Digital-Coded Squelch System). The use of digital squelch on a channel that has existing tone squelch users
224:
console, a microphone may have a split push-to-talk button. Pressing one half of the button, (often marked with a speaker icon or the letters "MON", short for "MONitor") disables the CTCSS decoder and reverts the receiver to hearing any signal on the channel. This is called the
274:
trigger. The user occasionally hears a syllable or two of co-channel users on a different CTCSS tone talking. As electronic components age, or through production variances, some radios in a system may be better than others at rejecting nearby tone frequencies.
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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
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precludes the use of the 131.8 and 136.5 Hz tones as the digital bit rate is 134.4 bits per second and the decoders set to those two tones will sense an intermittent signal (referred to in the two-way radio field as "falsing" the decoder).
213:. For example, in a 5 kHz deviation system, the CTCSS tone level would normally be set to 750 Hz deviation. Engineered systems may call for different level settings in the 500 Hz to 1 kHz (10–20%) range.
1138:
be present and may block the receiver, but the decoder will prevent it from being heard. It will still degrade system performance but the user will not have to hear the noises produced by receiving the interference.
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function. There is sometimes a mechanical interlock: the user must push down and hold the monitor button or the transmit button is locked and cannot be pressed. This interlock option is referred to as
193:
Radio transmitters using CTCSS always transmit their own tone code whenever the transmit button is pressed. The tone is transmitted at a low level simultaneously with the voice. This is called CTCSS
1145:
operations for this purpose. Wideband and extremely sensitive radios are common in the amateur radio field, which imposes limits on achievable intermodulation and adjacent-channel performance.
1005:
Non-standard numerical codes. Many radios use a matching set of numerical codes to represent corresponding tones; however, there is no published standard and only partial industry adoption.
162:
for
Private Line, a trademark of Motorola. It does this by adding a low frequency audio tone to the voice. Where more than one group of users is on the same radio frequency (called
55:
173:, but this is a misnomer because no additional radio channels are created. All users with different CTCSS tones on the same channel are still transmitting on the identical
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to monitor. Some modern radios have a feature called "Busy
Channel Lockout", which will not allow the user to transmit as long as the radio is receiving another signal.
102:
1435:
986:
74:
81:
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indicator may glow green, yellow, or orange to indicate another user is talking on the channel. Hand-held radios usually have a switch or
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Some radios use 69.4 Hz instead, which better fits the harmonic sequence, and this tone is often omitted as a choice.
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Many NATO military radios have a switchable 150.0 Hz tone. The list includes the following radios: AN/PRC-68,
95:
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The ability of a receiver to mute the audio until it detects a carrier with the correct CTCSS tone is called
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985:. The full list of the tones can be found in their original standard RS-220A, and the most recent EIA/
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The 8Z, 9Z, and 0Z ("zero-Z") tones are often omitted from radios that use the M1–M7 series of tones.
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Land Mobile FM or PM – Communications
Equipment – Measurement and Performance Standards, TIA-603-E
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tone is present, the receiver is unmuted, when it is not present the receiver is silent.
209:. In an FM two-way radio system, CTCSS encoder levels are usually set for 15% of system
166:), CTCSS circuitry mutes those users who are using a different CTCSS tone or no CTCSS.
1604:
1255:(Technical report). Telecommunications Industry Association. March 2, 2016. p. 10.
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220:. Receivers are equipped with features to allow the CTCSS "lock" to be disabled. On a
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233:(the user is forced to monitor by the hardware design of the equipment itself). On
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that is used to reduce the annoyance of listening to other users on a shared
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EIA Standard RS-220-A, Continuous Tone-Controlled
Squelch Systems (CTCSS)
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1296:"Information Sheet: Continuous Tone Controlled Squelch System"
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31:
1218:"A Historical and Technical Overview of Tone Squelch Systems"
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filtered out before being sent to the speaker or headphone.
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communication channel. It is sometimes referred to as
1102:
Non-standard tone not included in current TIA-603-E.
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1344:. American Radio Relay League. pp. 2-12–2-13.
62:. Unsourced material may be challenged and removed.
1192:"No Nonsense Technician Class License Study Guide"
1320:Explanation of Reverse Burst & "And Squelch"
169:CTCSS tone codes are sometimes referred to as
1429:
8:
1342:The ARRL Operating Manual for Radio Amateurs
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1422:
1414:
305:
1369:. John Wiley & Sons. pp. 62–64.
122:Learn how and when to remove this message
180:A receiver with just a carrier or noise
1367:Two-Way Radios and Scanners for Dummies
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998:
205:. The tones are usually referred to as
1141:CTCSS is commonly used in VHF and UHF
71:"Continuous Tone-Coded Squelch System"
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7:
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981:CTCSS tones are standardized by the
140:Continuous Tone-Coded Squelch System
60:adding citations to reliable sources
1392:"CTCSS Compatibility in FRS Radios"
1390:Eisner, Robert H. (July 23, 1999).
1278:"CTCSS Compatibility in FRS Radios"
1190:Romanchik, Dan (February 4, 2022).
289:CTCSS is an analog system. A later
231:compulsory monitor before transmit
25:
1547:Common traffic advisory frequency
1216:Morris, Mike (January 29, 2013).
1266:List of non-standard CTCSS codes
36:
47:needs additional citations for
1171:Signaling (telecommunications)
293:(DCS) system was developed by
1:
1656:Maritime mobile amateur radio
1340:Wilson, Mark J., ed. (2007).
1799:Voting (diversity combining)
1537:Aircraft emergency frequency
1484:General Mobile Radio Service
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1825:Telecommunication protocols
1552:Mandatory frequency airport
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27:Type of additive noise gate
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1744:Automatic vehicle location
1054:, AN/PRC-137, AN/PRC-139,
1023:Also known by the code SP.
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201:range from 67 to 257
1769:Dynamic range compression
1686:Dual-tone multi-frequency
1600:Professional mobile radio
1562:Single Frequency Approach
1326:January 19, 2008, at the
1794:Radiotelephony procedure
1610:Specialized Mobile Radio
1365:Silver, H. Ward (2011).
1166:Radiotelephony procedure
320:
317:
314:
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1504:Multi-Use Radio Service
1330:- Kevin K. Custer W3KKC
1066:, AN/PSC-5, and Thales
1576:Land-based commercial
1464:Amateur radio repeater
1284:on September 24, 2001.
1133:Interference and CTCSS
1578:and government mobile
1525:(aeronautical mobile)
1398:on September 27, 2014
291:Digital-Coded Squelch
279:Digital-Coded Squelch
1615:Trunked radio system
1479:Public Radio Service
1474:Family Radio Service
1452:Amateur and hobbyist
1149:Family Radio Service
56:improve this article
1646:Coast radio station
1532:Air traffic control
1469:Citizens band radio
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189:Theory of operation
1629:Marine (shipboard)
1514:UHF CB (Australia)
306:
285:Squelch § DCS
136:telecommunications
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1668:Selective calling
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207:sub-audible tones
148:in-band signaling
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16:(Redirected from
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1820:Radio technology
1725:System elements
1651:Marine VHF radio
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1394:. Archived from
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1280:. Archived from
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1068:AN/PRC-148 MBITR
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164:co-channel users
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1677:
1674:
1673:
1671:
1669:
1663:
1657:
1654:
1652:
1649:
1647:
1644:
1642:
1639:
1637:
1634:
1633:
1631:
1627:
1621:
1620:Walkie-talkie
1618:
1616:
1613:
1611:
1608:
1606:
1603:
1601:
1598:
1596:
1593:
1591:
1590:Business band
1588:
1586:
1583:
1582:
1580:
1574:
1568:
1565:
1563:
1560:
1558:
1555:
1553:
1550:
1548:
1545:
1543:
1540:
1538:
1535:
1533:
1530:
1529:
1527:
1521:
1515:
1512:
1510:
1507:
1505:
1502:
1500:
1497:
1495:
1492:
1490:
1487:
1485:
1482:
1480:
1477:
1475:
1472:
1470:
1467:
1465:
1462:
1460:
1459:Amateur radio
1457:
1456:
1454:
1450:
1446:
1445:Two-way radio
1439:
1434:
1432:
1427:
1425:
1420:
1419:
1416:
1397:
1393:
1386:
1383:
1378:
1372:
1368:
1361:
1358:
1353:
1347:
1343:
1336:
1333:
1329:
1325:
1322:
1321:
1315:
1312:
1297:
1291:
1288:
1283:
1279:
1273:
1270:
1267:
1262:
1259:
1254:
1248:
1245:
1241:. March 1979.
1240:
1234:
1231:
1219:
1212:
1209:
1197:. p. 121
1193:
1186:
1183:
1176:
1172:
1169:
1167:
1164:
1163:
1159:
1157:
1154:
1150:
1146:
1144:
1143:amateur radio
1139:
1132:
1130:
1124:Reverse CTCSS
1123:
1113:
1111:
1109:
1105:
1099:
1097:
1095:
1093:
1091:
1089:
1087:
1085:
1083:
1081:
1079:
1077:
1073:
1069:
1065:
1061:
1057:
1053:
1049:
1045:
1039:
1036:
1029:
1026:
1020:
1017:
1011:
1008:
1002:
999:
992:
990:
988:
984:
975:
965:
962:
952:
949:
939:
936:
926:
923:
913:
910:
900:
897:
887:
884:
874:
871:
861:
858:
848:
845:
840:
836:
833:
828:
824:
821:
811:
808:
803:
799:
796:
786:
783:
778:
774:
771:
761:
758:
753:
749:
746:
736:
733:
728:
724:
721:
711:
708:
703:
699:
696:
686:
683:
678:
674:
671:
661:
658:
648:
645:
640:
636:
633:
623:
620:
610:
607:
597:
594:
584:
581:
571:
568:
558:
555:
545:
542:
532:
529:
519:
516:
506:
503:
493:
490:
480:
477:
467:
464:
454:
451:
441:
438:
428:
425:
415:
412:
402:
399:
389:
386:
376:
373:
363:
360:
350:
347:
337:
334:
324:
310:
302:List of tones
301:
299:
296:
292:
286:
278:
276:
273:
270:periodically
267:
263:
260:
254:
250:
248:
244:
240:
236:
235:mobile radios
232:
228:
223:
219:
214:
212:
208:
204:
200:
196:
188:
186:
183:
178:
176:
172:
167:
165:
161:
157:
153:
152:two-way radio
149:
145:
141:
137:
126:
123:
115:
112:December 2021
104:
101:
97:
94:
90:
87:
83:
80:
76:
73: –
72:
68:
67:Find sources:
61:
57:
51:
50:
45:This article
43:
39:
34:
33:
30:
19:
1706:Quik-Call II
1696:Push-to-talk
1675:
1666:Signaling /
1595:Mobile radio
1585:Base station
1400:. Retrieved
1396:the original
1385:
1366:
1360:
1341:
1335:
1319:
1314:
1302:. Retrieved
1290:
1282:the original
1272:
1261:
1252:
1247:
1238:
1233:
1221:. Retrieved
1211:
1199:. Retrieved
1185:
1147:
1140:
1136:
1127:
1038:
1028:
1019:
1010:
1001:
980:
307:CTCSS tones
288:
268:
264:
255:
251:
230:
226:
222:base station
217:
215:
206:
194:
192:
179:
171:sub-channels
170:
168:
163:
159:
156:tone squelch
155:
143:
139:
133:
118:
109:
99:
92:
85:
78:
66:
54:Please help
49:verification
46:
29:
1789:Tone remote
1779:Link budget
1774:Fade margin
1701:Quik-Call I
1402:January 23,
1044:AN/PRC-117F
247:push-button
241:radios, an
1814:Categories
1499:Mobile rig
1376:1118054601
1351:0872591093
1201:August 19,
1177:References
1060:AN/PRC-119
1056:AN/PRC-152
1052:AN/PRC-113
82:newspapers
1759:DC remote
1749:Call sign
1523:Aviation
1064:AN/VRC-12
1048:AN/PRC-77
239:hand-held
211:deviation
1764:Dispatch
1691:MDC-1200
1636:2182 kHz
1557:MULTICOM
1324:Archived
1223:March 6,
1160:See also
295:Motorola
259:repeater
218:decoding
197:. CTCSS
195:encoding
1734:Antenna
1711:Selcall
1641:500 kHz
1542:Airband
1489:KDR 444
1304:July 8,
1151:(FRS),
983:EIA/TIA
227:monitor
182:squelch
96:scholar
1716:SELCAL
1681:D-STAR
1567:UNICOM
1509:PMR446
1494:LPD433
1373:
1348:
1153:PMR446
973:254.1
960:250.3
947:241.8
934:233.6
921:229.1
908:225.7
895:218.1
882:210.7
869:206.5
856:203.5
843:199.5
831:196.6
819:192.8
806:189.9
794:186.2
781:183.5
769:179.9
756:177.3
744:173.8
731:171.3
719:167.9
706:165.5
694:162.2
681:159.8
669:156.7
656:151.4
643:150.0
631:146.2
618:141.3
605:136.5
592:131.8
579:127.3
566:123.0
553:118.8
540:114.8
527:110.9
514:107.2
501:103.5
488:100.0
321:Notes
98:
91:
84:
77:
69:
1676:CTCSS
1299:(PDF)
1195:(PDF)
1033:used.
993:Notes
638:NATO
475:97.4
462:94.8
449:91.5
436:88.5
423:85.4
410:82.5
397:79.7
384:77.0
371:74.4
358:71.9
345:69.3
332:67.0
272:false
199:tones
144:CTCSS
103:JSTOR
89:books
18:CTCSS
1739:APRS
1404:2023
1371:ISBN
1346:ISBN
1306:2019
1225:2013
1203:2023
312:NS
75:news
1754:CAD
987:TIA
970:0Z
967:50
957:M7
954:38
944:M6
941:37
931:M5
928:36
918:9Z
915:49
905:M4
902:35
892:M3
889:34
879:M2
876:33
866:8Z
863:48
853:M1
850:32
838:47
826:46
816:7A
813:31
801:45
791:7Z
788:30
776:44
766:6B
763:29
751:43
741:6A
738:28
726:42
716:6Z
713:27
701:41
691:5B
688:26
676:40
666:5A
663:25
653:5Z
650:24
628:4B
625:23
615:4A
612:22
602:4Z
599:21
589:3B
586:20
576:3A
573:19
563:3Z
560:18
550:2B
547:17
537:2A
534:16
524:2Z
521:15
511:1B
508:14
498:1A
495:13
485:1Z
482:12
472:ZB
469:11
459:ZA
456:10
446:ZZ
433:YB
420:YA
407:YZ
394:WB
381:XB
368:WA
355:XA
342:WZ
339:39
329:XZ
318:Hz
315:PL
243:LED
158:or
142:or
134:In
58:by
1816::
1107:^
1075:^
1062:,
1058:,
1050:,
443:9
430:8
417:7
404:6
391:5
378:4
365:3
352:2
326:1
203:Hz
160:PL
138:,
1437:e
1430:t
1423:v
1406:.
1379:.
1354:.
1308:.
1227:.
1205:.
1070:.
125:)
119:(
114:)
110:(
100:·
93:·
86:·
79:·
52:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
