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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
113:), 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.
552:(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.
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190:. 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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574:(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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696:. 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
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over the same channel as the bearer channel used for voice traffic.
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669:"NENA 03-002 v2: Enhanced MF Signaling, E9-1-1 Tandem to PSAP"
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Multifrequency signaling is a technological precursor of
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published the following standards for MF tone timing:
53:. It uses a combination of audible tones for address (
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653:: CS1 maint: bot: original URL status unknown (
578:'D' (101xxxx) alternate long-distance provider.
61:between central offices. The signaling is sent
630:"In-Band Signaling in the former Soviet Union"
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548:In-band signaling fell into disfavor in the
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636:. Archived from the original on 2021-05-16
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57:) transport and supervision signaling on
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149:How multi-frequency dialing sounds.
107:dual-tone multi-frequency signaling
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572:Mobile Telephone Switching Offices
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157:Problems playing this file? See
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736:Signaling (telecommunications)
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568:Public Safety Answering Points
175:. MF is used for signaling in
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615:Telecommunications Switching
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45:that was introduced by the
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612:Pearce, J. Gordon (2013).
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618:. Springer. p. 243.
557:Common Channel Signaling
169:multi-frequency receiver
817:Signalling System No. 7
812:Signalling System No. 6
694:direct distance dialing
207:Multifrequency signals
202:Multi-frequency signals
135:Multi-frequency dialing
98:with devices such as a
77:Regional Standard No. 1
807:Signaling System No. 5
588:Signaling System No. 5
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835:Telephones portal
532:Digits 0-9, ST: 55 ms
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593:Two-out-of-five code
85:Signalling System R2
81:Signalling System R1
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89:Signalling System 7
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173:telephone exchange
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854:Telephony signals
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686:"Speeding Speech"
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638:. Retrieved
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218:900 Hz
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51:World War II
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762:Busy signal
690:Bell System
529:KP (110 ms)
523:Bell System
59:trunk lines
47:Bell System
688:, a 1950s
640:2019-08-08
599:References
159:media help
111:Touch-Tone
747:Dial tone
566:Most 911
192:phreaking
117:Operation
43:signaling
31:telephony
848:Category
787:Zip tone
752:Ringtone
649:cite web
582:See also
196:blue box
177:trunking
100:blue box
792:2600 Hz
444:12/ST2
425:11/ST3
194:with a
109:(DTMF,
64:in-band
544:Demise
49:after
406:0/10
212:Code
79:, or
73:CCITT
655:link
521:The
482:KP2
501:ST
463:KP
29:In
850::
651:}}
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102:.
39:MF
33:,
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37:(
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