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sends address information to the terminating switch. In R1 MF signaling this address information normally is a KP tone, the numeric digits of the destination number, and an ST tone to indicate the end of the address. Other information may also be added, such as the caller's number, using KP2 as a delimiter.
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Using MF signaling, the originating telephone switch sends a start signal to seize the line, taking the circuit off-hook. The terminating office acknowledges the seizure with a ready state by responding with a wink start signal, which is a momentary off-hook condition. The originating office then
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Multi-frequency signaling defines electronic signals that consist of a combination of two audible frequencies, usually selected from a set of six frequencies. Over several decades, various types of MF signaling were developed, including national and international varieties. The
102:), which uses the same fundamental principle, but was used primarily for signaling address information and control signals from a user's telephone to the wire-center's Class-5 switch. DTMF uses a total of eight frequencies.
541:(PSTN) as electronic switching systems displaced electro-mechanical switching systems, but legacy offices may still exist in some countries that are still using some electromechanical and other legacy switching equipment.
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Digits are represented by two simultaneous tones selected from a set of five (MF 2/5), six (MF 2/6), or eight (MF 2/8) frequencies. The frequency combinations are played, one at a time for each digit, to the remote
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These standards are, for the most part, still in place where MF signaling is in use in legacy exchanges. MF signaling is still used in North
America for inter-office signaling, although it is increasingly rare.
179:. Depending on the type and configuration of switching equipment, it may or may not be audible to the telephone user, but the technology was vulnerable to abuse with a method called
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563:(MTSOs) and landline telephone exchanges. This is based on an earlier system which used MF to identify the calling party to a
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film, depicts a 2-1-1 long-distance operator manually entering a number on an MF keypad just prior to the introduction of
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Because of the in-band transmission characteristic of MF signaling, the systems proved vulnerable to misuse and fraud by
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685:. The keypad, visible at 0:01:41 and 0:05:20, has two columns of five digits plus KP (key pulse) and ST (start).
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which generates the tones required to control remote telephone switches.
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The interval between digits is the same as the digit duration (55 ms)
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standardization process specified the
American Bell System version as
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Details of MF signaling from Bell
Laboratories Record. Pages 221-225
548:(CCS) became nearly universal by the end of the 20th century in the
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over the same channel as the bearer channel used for voice traffic.
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658:"NENA 03-002 v2: Enhanced MF Signaling, E9-1-1 Tandem to PSAP"
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Multifrequency signaling is a technological precursor of
76:. Both were largely replaced by digital systems, such as
80:, which operate out-of-band on a separate data network.
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published the following standards for MF tone timing:
42:. It uses a combination of audible tones for address (
642:: CS1 maint: bot: original URL status unknown (
567:'D' (101xxxx) alternate long-distance provider.
50:between central offices. The signaling is sent
619:"In-Band Signaling in the former Soviet Union"
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537:In-band signaling fell into disfavor in the
72:, and a corresponding European standard as
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625:. Archived from the original on 2021-05-16
46:) transport and supervision signaling on
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138:How multi-frequency dialing sounds.
96:dual-tone multi-frequency signaling
561:Mobile Telephone Switching Offices
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539:public switched telephone network
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146:Problems playing this file? See
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725:Signaling (telecommunications)
557:Public Safety Answering Points
164:. MF is used for signaling in
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604:Telecommunications Switching
34:that was introduced by the
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601:Pearce, J. Gordon (2013).
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791:Multi-frequency signaling
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607:. Springer. p. 243.
546:Common Channel Signaling
158:multi-frequency receiver
801:Signalling System No. 7
683:direct distance dialing
196:Multifrequency signals
191:Multi-frequency signals
124:Multi-frequency dialing
87:with devices such as a
66:Regional Standard No. 1
796:Signaling System No. 5
577:Signaling System No. 5
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819:Telephones portal
521:Digits 0-9, ST: 55 ms
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582:Two-out-of-five code
74:Signalling System R2
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78:Signalling System 7
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756:Reorder tone
746:Ringing tone
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627:. Retrieved
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544:Out-of-band
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207:900 Hz
204:700 Hz
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40:World War II
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751:Busy signal
679:Bell System
518:KP (110 ms)
512:Bell System
48:trunk lines
36:Bell System
677:, a 1950s
629:2019-08-08
588:References
148:media help
100:Touch-Tone
736:Dial tone
555:Most 911
181:phreaking
106:Operation
32:signaling
20:telephony
832:Category
776:Zip tone
741:Ringtone
638:cite web
571:See also
185:blue box
166:trunking
89:blue box
781:2600 Hz
433:12/ST2
414:11/ST3
183:with a
98:(DTMF,
53:in-band
533:Demise
38:after
395:0/10
201:Code
68:, or
62:CCITT
644:link
510:The
471:KP2
490:ST
452:KP
18:In
834::
640:}}
636:{{
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91:.
28:MF
22:,
717:e
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26:(
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