811:(Selective Calling) transmits a burst of up to five in-band audio tones at the beginning of each transmission. This feature (sometimes called "tone burst") is common in European systems. Early systems used one tone (commonly called "Tone Burst"). Several tones were used, the most common being 1,750 Hz, which is still used in European amateur radio repeater systems. The addressing scheme provided by one tone was not enough, so a two-tone system was devised—one tone followed by a second tone (sometimes called a "1+1" system). Motorola later marketed a system called "Quik-Call" that used two simultaneous tones followed by two more simultaneous tones (sometimes called a "2+2" system) that was heavily used by fire department dispatch systems in the US. Later selective call systems used paging system technology that made use of a burst of five sequential tones.
207:), the received signal level required to unsquelch (un-mute) the receiver may be fixed or adjustable with a knob or a sequence of button presses. Typically the operator will adjust the control until noise is heard, and then adjust in the opposite direction until the noise is squelched. At this point, a weak signal will unsquelch the receiver and be heard by the operator. Further adjustment will increase the level of signal required to unsquelch the receiver. Some applications have the receiver tied to other equipment that uses the audio muting control voltage, as a "signal present" indication; for example, in a
32:
181:
413:. There are many other company-specific names used by radio vendors to describe compatible options. Any CTCSS system that has compatible tones is interchangeable. Old and new radios with CTCSS and radios across manufacturers are compatible. For those PMR446 radios with 38 codes, the codes 0 to 38 are CTCSS Tones:
332:
users), selective calling addresses a subset of all receivers. Instead of turning on the receiver audio for any signal, the audio turns on only in the presence of the correct selective calling code. This is akin to the use of a lock on a door. A carrier squelch is unlocked and will let any signal in.
336:
In non-critical uses, selective calling can also be used to hide the presence of interfering signals such as receiver-produced intermodulation. Receivers with poor specifications—such as inexpensive police scanners or low-cost mobile radios—cannot reject the strong signals present in urban
1263:(23,12) code which has the ability to detect and correct errors of 3 or fewer bits. The word consists of 12 data bits followed by 11 check bits. The last 3 data bits are a fixed '001', this leaves 9 code bits (512 possibilities) which are conventionally represented as a 3-digit
2051:
is the newest signalling technique, and provides 99 codes with the added advantage of "silent operation". XTCSS-fitted radios are purposed to enjoy more privacy and flexibility of operation. XTCSS is implemented as a combination of CTCSS and in-band signalling.
270:
circuit is noise-operated and can be used in AM or FM receivers, and relies on the receiver quieting in the presence of an AM or FM carrier. To minimize the effects of voice audio on squelch operation, the audio from the receiver's detector is passed through a
1228:(Continuous Digital-Coded Squelch System), was designed as the digital replacement for CTCSS. In the same way that a single CTCSS tone would be used on an entire group of radios, the same DCS code is used in a group of radios. DCS is also referred to as
2068:. Since a carrier squelch receiver cannot tell a valid carrier from a spurious signal (noise, etc.), CTCSS is often used as well, as it avoids false keyups. Use of CTCSS is especially helpful on congested frequencies or on frequency bands prone to
295:
is present. The presence of continuous noise on an idle channel creates a DC voltage which turns the receiver audio off. When a signal with little or no noise is received, the noise-derived voltage is reduced and the receiver audio is unmuted.
2079:
use squelch to avoid reproducing noise when the receiver does not receive enough signal from the microphone. Most professional models have adjustable squelch, usually set with a screwdriver adjustment or front-panel control on the receiver.
1267:
number. Note that the first bit transmitted is the LSB, so the code is "backwards" from the transmitted bit order. Only 83 of the 512 possible codes are available, to prevent falsing due to alignment collisions.
337:
environments. The interference will still be present, and will still degrade system performance, but by using selective calling the user will not have to hear the noises produced by receiving the interference.
215:(turned off), which allows all signals to be heard, including radio frequency noise on the receiving frequency. This can be useful when trying to hear distant or otherwise weak signals, for example in
1275:
with the following 83 codes being found in their most recent standard, however, some systems use non-standard codes. For those PMR446 radios with 121 codes, the codes 39 to 121 are DCS codes:
1252:, and other names by other manufacturers. Radios with DCS options are generally compatible, provided the radio's encoder-decoder will use the same code as radios in the existing system.
2164:
2060:
Squelch was invented first and is still in wide use in two-way radio. Squelch of any kind is used to indicate loss of signal, which is used to keep commercial and
328:
Tone squelch, or another form of selective calling, is sometimes used to solve interference problems. Where more than one user is on the same channel (
2210:
2150:
1272:
2599:
188:
In some designs, the squelch threshold is preset. For example, television squelch settings are usually preset. Receivers in
2450:
353:
2460:
369:. The original tone set was 10, then 32 tones, and has been expanded even further over the years. CTCSS is often called
275:, typically passing 4,000 Hz (4kHz) and above, leaving only high frequency noise. The squelch control adjusts the
96:
2513:
2321:
115:
68:
75:
53:
2430:
2273:
2311:
2258:
1236:), another trademark of Motorola, and likewise, General Electric's implementation of DCS is referred to as
2480:
2326:
2203:
333:
Selective calling locks out all signals except ones with the correct key to the lock (the correct code).
82:
2594:
2518:
253:
2543:
2374:
2336:
2125:
361:(Continuous Tone-Coded Squelch System) continuously superimposes any one of about 50 low-pitch audio
137:
64:
2568:
2384:
49:
20:
2147:
Land Mobile FM or PM – Communications
Equipment – Measurement and Performance Standards, TIA-603-E
306:
present in the high-pass band. For this reason, many receivers with noise squelch will also use a
2528:
2475:
2278:
42:
2238:
2196:
2061:
249:
237:
2533:
2089:
340:
Four different techniques are commonly used. Selective calling can be regarded as a form of
2538:
2389:
2253:
2248:
2119:
196:
at remote mountain top sites, are usually not adjustable remotely from the control point.
8:
2573:
2420:
2306:
2243:
2076:
169:
2171:
276:
141:
129:
2440:
1260:
1249:
341:
323:
89:
2425:
390:
292:
272:
149:
2558:
2508:
1256:
303:
226:
211:
the act of the receiver unmuting will switch on the transmitter. Squelch can be
2379:
288:
204:
2588:
2394:
2364:
2233:
2219:
362:
241:
200:
165:
161:
1259:(sub-audible) bitstream to the transmitted audio. The code word is a 23-bit
283:
which varies the level of the noise coming out of the filter. This noise is
2470:
2369:
2359:
2069:
2065:
189:
2563:
2553:
2548:
2094:
230:
157:
2523:
378:
284:
280:
31:
2465:
2410:
2331:
382:
208:
193:
2485:
2415:
2316:
2263:
803:
233:
2188:
225:
is the most simple variant of all. It functions strictly on the
2490:
2455:
2341:
2288:
2283:
2268:
153:
1244:). Despite the fact that it is not a tone, DCS is also called
1264:
366:
216:
145:
180:
402:
172:
when the radio is not receiving a desired transmission.
160:
designed to suppress weak signals. Squelch is used in
2124:(3rd ed.). American Radio Relay League. p.
317:
56:. Unsourced material may be challenged and removed.
365:on the transmitted signal, ranging from 67 to 254
2586:
156:. Essentially, squelch is a specialized type of
1224:(Digital-Coded Squelch), generically known as
2204:
244:mutes the audio when no signal is present.
2211:
2197:
252:(AGC) to determine the squelch threshold.
266:is more reliable than carrier squelch. A
236:the audio or blanks the video on "empty"
116:Learn how and when to remove this message
179:
2151:Telecommunications Industry Association
1273:Telecommunications Industry Association
2587:
2192:
393:'s implementation of CTCSS is called
354:Continuous Tone-Coded Squelch System
54:adding citations to reliable sources
25:
310:set at a higher threshold than the
140:function that acts to suppress the
13:
1271:DCS codes are standardized by the
318:Tone squelch and selective calling
14:
2611:
2322:Common traffic advisory frequency
2218:
2121:The ARRL Ham Radio License Manual
152:in the absence of a strong input
30:
1248:(Digital Tone Code Squelch) by
41:needs additional citations for
2157:
2139:
2112:
1:
2431:Maritime mobile amateur radio
2105:
2600:Telecommunications equipment
2574:Voting (diversity combining)
2312:Aircraft emergency frequency
2259:General Mobile Radio Service
2153:. March 2, 2016. p. 10.
7:
2327:Mandatory frequency airport
2083:
10:
2616:
2519:Automatic vehicle location
2072:and during band openings.
801:
797:
420:PMR446 CTCSS Privacy Codes
351:
321:
254:Single-sideband modulation
175:
168:to eliminate the sound of
18:
2544:Dynamic range compression
2499:
2461:Dual-tone multi-frequency
2439:
2403:
2375:Professional mobile radio
2350:
2337:Single Frequency Approach
2297:
2226:
859:
854:
849:
844:
839:
834:
829:
824:
418:
2569:Radiotelephony procedure
2385:Specialized Mobile Radio
2165:"TLKR T8 Owner's Manual"
2100:
2043:
347:
21:Attenuator (electronics)
19:Not to be confused with
2279:Multi-Use Radio Service
2062:amateur radio repeaters
2055:
2351:Land-based commercial
2239:Amateur radio repeater
1255:DCS adds a 134.4
814:
250:Automatic gain control
185:
2353:and government mobile
2300:(aeronautical mobile)
2090:Dynamic noise limiter
1238:Digital Channel Guard
749: 97.4
723: 94.8
697: 91.5
671: 88.5
645: 85.4
619: 82.5
593: 79.7
567: 77.0
541: 74.4
515: 71.9
489: 67.0
256:(SSB) typically uses
183:
2390:Trunked radio system
2254:Public Radio Service
2249:Family Radio Service
2227:Amateur and hobbyist
2149:(Technical report).
2077:wireless microphones
1230:Digital Private Line
50:improve this article
2421:Coast radio station
2307:Air traffic control
2244:Citizens band radio
1282:
821:
820:Standard DCS Codes
791: 250.3
783: 156.7
765: 241.8
757: 151.4
739: 233.6
731: 146.2
713: 225.7
705: 141.3
687: 218.1
679: 136.5
661: 210.7
653: 131.8
635: 203.5
627: 127.3
609: 192.8
601: 123.0
583: 186.2
575: 118.8
557: 179.9
549: 114.8
531: 173.8
523: 110.9
505: 167.9
497: 107.2
479: 162.2
302:can be defeated by
184:A squelch threshold
2404:Marine (shipboard)
2289:UHF CB (Australia)
2172:Motorola Solutions
1278:
819:
186:
130:telecommunications
16:Type of noise gate
2595:Radio electronics
2582:
2581:
2443:Selective calling
2064:from continually
2041:
2040:
1219:
1218:
795:
794:
342:in-band signaling
324:Selective calling
229:, such as when a
126:
125:
118:
100:
2607:
2500:System elements
2426:Marine VHF radio
2213:
2206:
2199:
2190:
2189:
2183:
2182:
2180:
2179:
2169:
2161:
2155:
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2143:
2137:
2136:
2134:
2132:
2116:
1283:
1277:
822:
818:
416:
415:
391:General Electric
273:high-pass filter
121:
114:
110:
107:
101:
99:
58:
34:
26:
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2559:Rayleigh fading
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2086:
2058:
2046:
817:
806:
800:
775: 100.0
471: 103.5
403:RCA Corporation
356:
350:
326:
320:
308:carrier squelch
304:intermodulation
258:carrier squelch
246:Carrier squelch
227:signal strength
223:Carrier squelch
205:radiotelephones
203:(also known as
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405:used the name
352:Main article:
349:
346:
322:Main article:
319:
316:
287:, producing a
248:uses receiver
201:two-way radios
177:
174:
166:radio scanners
162:two-way radios
148:) output of a
124:
123:
106:September 2019
38:
36:
29:
15:
9:
6:
4:
3:
2:
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2419:
2417:
2414:
2412:
2409:
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2402:
2396:
2395:Walkie-talkie
2393:
2391:
2388:
2386:
2383:
2381:
2378:
2376:
2373:
2371:
2368:
2366:
2365:Business band
2363:
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2257:
2255:
2252:
2250:
2247:
2245:
2242:
2240:
2237:
2235:
2234:Amateur radio
2232:
2231:
2229:
2225:
2221:
2220:Two-way radio
2214:
2209:
2207:
2202:
2200:
2195:
2194:
2191:
2173:
2166:
2160:
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2148:
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2127:
2123:
2122:
2115:
2111:
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2087:
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2078:
2075:Professional
2073:
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2037:
2035:
2032:
2030:
2027:
2024:
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407:Quiet Channel
404:
400:
396:
395:Channel Guard
392:
388:
385:), or simply
384:
380:
376:
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368:
364:
360:
355:
345:
343:
338:
334:
331:
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315:
313:
312:noise squelch
309:
305:
301:
300:Noise squelch
297:
294:
290:
286:
282:
278:
274:
269:
268:noise squelch
265:
264:Noise squelch
261:
259:
255:
251:
247:
243:
242:walkie-talkie
239:
235:
232:
228:
224:
220:
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202:
197:
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191:
190:base stations
182:
173:
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120:
117:
109:
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88:
84:
81:
77:
74:
70:
67: –
66:
62:
61:Find sources:
55:
51:
45:
44:
39:This article
37:
33:
28:
27:
22:
2481:Quik-Call II
2471:Push-to-talk
2441:Signaling /
2370:Mobile radio
2360:Base station
2176:. Retrieved
2174:. p. 19
2159:
2146:
2141:
2131:September 8,
2129:. Retrieved
2120:
2114:
2074:
2066:transmitting
2059:
2048:
2047:
2028:
2020:
2010:
2002:
1994:
1984:
1976:
1968:
1958:
1950:
1942:
1932:
1924:
1916:
1906:
1898:
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1301:
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1233:
1229:
1225:
1221:
1220:
860:
855:
850:
845:
840:
835:
830:
825:
808:
807:
786:
778:
770:
760:
752:
744:
734:
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718:
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692:
682:
674:
666:
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640:
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614:
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492:
484:
474:
466:
458:
451:
446:
441:
436:
431:
426:
419:
410:
406:
398:
394:
387:tone squelch
386:
375:Private Line
374:
370:
358:
357:
339:
335:
329:
327:
311:
307:
299:
298:
267:
263:
262:
257:
245:
240:, or when a
222:
221:
212:
198:
187:
164:and VHF/UHF
133:
127:
112:
103:
93:
86:
79:
72:
60:
48:Please help
43:verification
40:
2564:Tone remote
2554:Link budget
2549:Fade margin
2476:Quik-Call I
2589:Categories
2274:Mobile rig
2178:2023-01-23
2106:References
2095:Noise gate
330:co-channel
289:DC voltage
231:television
158:noise gate
76:newspapers
2534:DC remote
2524:Call sign
2298:Aviation
379:trademark
285:rectified
281:amplifier
194:repeaters
65:"Squelch"
2539:Dispatch
2466:MDC-1200
2411:2182 kHz
2332:MULTICOM
2084:See also
383:Motorola
238:channels
209:repeater
150:receiver
2509:Antenna
2486:Selcall
2416:500 kHz
2317:Airband
2264:KDR 444
1312:Tone Hz
1302:Tone Hz
1292:Tone Hz
809:Selcall
804:Selcall
798:SelCall
452:Tone Hz
442:Tone Hz
432:Tone Hz
371:PL tone
176:Squelch
138:circuit
134:squelch
90:scholar
2491:SELCAL
2456:D-STAR
2342:UNICOM
2284:PMR446
2269:LPD433
279:of an
213:opened
154:signal
92:
85:
78:
71:
63:
2451:CTCSS
2168:(PDF)
2101:Notes
2049:XTCSS
2044:XTCSS
1265:octal
1261:Golay
1257:bit/s
1226:CDCSS
409:, or
373:(for
363:tones
359:CTCSS
348:CTCSS
293:noise
291:when
234:mutes
217:DXing
192:, or
170:noise
146:video
142:audio
136:is a
97:JSTOR
83:books
2514:APRS
2133:2019
2070:skip
2056:Uses
2033:432
2025:172
2015:754
2007:431
1999:165
1989:743
1981:423
1973:162
1963:734
1955:413
1947:156
1937:732
1929:412
1921:155
1911:731
1903:411
1895:152
1885:723
1877:371
1869:143
1859:712
1851:365
1843:134
1833:703
1825:364
1817:132
1807:664
1799:351
1791:131
1781:662
1773:346
1765:125
1755:654
1747:343
1739:116
1729:632
1721:331
1713:115
1703:631
1695:315
1687:114
1677:627
1669:311
1661:074
1651:624
1643:306
1635:073
1625:612
1617:271
1609:072
1599:606
1591:265
1583:071
1573:565
1565:263
1557:065
1547:546
1539:261
1531:054
1521:532
1513:251
1505:051
1495:516
1487:245
1479:047
1469:506
1461:244
1453:043
1443:503
1435:243
1427:032
1417:466
1409:226
1401:031
1391:465
1383:223
1375:026
1365:464
1357:205
1349:025
1339:445
1331:174
1323:023
1307:Code
1297:Code
1287:Code
1250:Icom
1246:DTCS
1240:(or
1232:(or
1068:754
1043:743
1018:734
992:732
966:731
940:723
914:712
888:703
463:Off
447:Code
437:Code
427:Code
397:(or
377:, a
277:gain
144:(or
69:news
2529:CAD
2126:123
2011:121
1985:120
1959:119
1933:118
1907:117
1881:116
1855:115
1829:114
1803:113
1777:112
1751:111
1725:110
1699:109
1673:108
1647:107
1621:106
1595:105
1569:104
1543:103
1517:102
1491:101
1465:100
1280:DCS
1242:DCG
1234:DPL
1222:DCS
1203:174
1184:172
1181:074
1164:165
1161:073
1144:162
1141:072
1126:271
1123:156
1120:071
1109:466
1106:371
1103:265
1100:155
1097:065
1090:664
1085:465
1082:365
1079:263
1076:152
1073:054
1065:662
1060:464
1057:364
1054:261
1051:143
1048:051
1040:654
1035:445
1032:351
1029:251
1026:134
1023:047
1015:632
1012:565
1009:432
1006:346
1003:245
1000:132
997:043
989:631
986:546
983:431
980:343
977:244
974:131
971:032
963:627
960:532
957:423
954:331
951:243
948:125
945:031
937:624
934:516
931:413
928:315
925:226
922:116
919:026
911:612
908:506
905:412
902:311
899:223
896:115
893:025
885:606
882:503
879:411
876:306
873:205
870:114
867:023
861:7nn
856:6nn
851:5nn
846:4nn
841:3nn
836:2nn
831:1nn
826:0nn
815:DCS
401:).
381:of
199:In
128:In
52:by
2591::
2170:.
2029:94
2021:66
2003:93
1995:65
1977:92
1969:64
1951:91
1943:63
1925:90
1917:62
1899:89
1891:61
1873:88
1865:60
1847:87
1839:59
1821:86
1813:58
1795:85
1787:57
1769:84
1761:56
1743:83
1735:55
1717:82
1709:54
1691:81
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1639:79
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1613:78
1605:50
1587:77
1579:49
1561:76
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1535:75
1527:47
1509:74
1501:46
1483:73
1475:45
1457:72
1449:44
1439:99
1431:71
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1413:98
1405:70
1397:42
1387:97
1379:69
1371:41
1361:96
1353:68
1345:40
1335:95
1327:67
1319:39
787:38
779:25
771:12
761:37
753:24
745:11
735:36
727:23
719:10
709:35
701:22
683:34
675:21
657:33
649:20
631:32
623:19
605:31
597:18
579:30
571:17
553:29
545:16
527:28
519:15
501:27
493:14
475:26
467:13
411:QC
399:CG
389:.
367:Hz
344:.
314:.
260:.
219:.
132:,
2212:e
2205:t
2198:v
2181:.
2135:.
693:9
667:8
641:7
615:6
589:5
563:4
537:3
511:2
485:1
459:0
119:)
113:(
108:)
104:(
94:·
87:·
80:·
73:·
46:.
23:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
