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parlance. The outgoing register transmits forward MF tones to the incoming register. The incoming register transmits backward MF tones to the outgoing register. The outgoing register detects backward MF tones arriving from the incoming register. The incoming register detects forward MF tones arriving from the outgoing register. The outgoing register transmits the first signal, but from that point forward the outgoing register merely passively responds to the prompting driven by each signal transmitted by the incoming register. (In apt modern-era
547:
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Those that use only the A bit, strongly resemble the analog electrical R2 line signalling, where each signal is a timed pulse that differs by length of time that the pulse is in the high voltage (i.e., one-valued bit) state before returning to the untimed resting voltage state (i.e., zero-valued bit). Those that use multiple bits to represent each signal usually are stateful in that time of exhibition of that bit pattern typically plays no role in conveying meaning.
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the set of explicit requests corresponding to each of the forward register-signalling data. The client–server requesting of each of these data differentiates R2 from the Bell System R1 MF-tone signalling, where in R1 the called-party's switch unilaterally sends some of these data as a timed sequence
349:
The
European market consisted of a large number of national telecommunications administrations, but unlike the Bell System, these were not usually integrated with an equipment manufacturer. Instead a large number of independent vendors of equipment emerged in Europe though the 20th century in a very
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form via the A, B, C, and D bits in DS0 channel #16 of an E1 fall into two general categories: those that use only the A bit to represent each signal and those that use multiple A, B, C, and D bits to represent each signal, with using only two, the A bit and the B bit being by far the most common.
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R2 line signalling is a family of protocols that govern the resource acquisition and resource release related to a two-party telephone call attempt and, if successful, the establishment of a two-party telephone call. Although in the 1960s R2 line signalling was represented as electrical pulses on a
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European equipment vendors such as
Ericsson, Siemens and the European ITT affiliates, amongst others became major suppliers to telecommunication administrations around the world bringing technologies like Ericsson’s ARF and ITT’s Pentaconta crossbars to many markets. European derived standards were
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tone, or MF tone. Each call attempt has an origination end and a termination end, both to the multi-span call as well as for each span within that multi-span call routing. The origination end is called the outgoing register in R2 parlance. The termination end is called the incoming register in R2
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R2 register signalling is a family of protocols that govern the conveyance of addressing information during the addressing phase and how the call attempt turned out during the disposition phase. Although in the 1960s R2 register signalling was represented by electromechanical devices that could
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The international version of R2 is an inter-nation protocol for R2 signalling that crosses national boundaries, and is neither a superset nor a subset of any national variant of R2. Conversely, each national variant of R2 is intra-nation. The international standard R2 was first promulgated by
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audio tones and by electromechanical devices that could detect those audio tones, by the latter 1970s these electromechanical registers also could be represented by digitized PCM audio in DS0 channels of an E1 other than the R2 line signalling DS0 channel in that E1.
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R2 signalling was also used for register signaling within many
European switching systems of that era, notably in Ericsson’s AR- crossbar systems. It was used for inter station communication and for communication between parent and remote switches.
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the release of the call (e.g., the handset of the called-party's telephone has now been returned to its on-hook position, ending this call; the telephone company or trouble in the network is explicitly or implicitly forcing the ending of this call)
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that was in use from the 1960s mostly in Europe, and later also in Latin
America, Asia, and Australia, to convey exchange information between two telephone switching systems for establishing a telephone call via a
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the called party has now lifted the handset from its hook to answer this call attempt in order to transition from R2 signalling toward the establishment of speech-capable audio to fully establish the call (termed
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R2 line signalling variants that support R2 line signalling in its electrical-pulse form by dedicated two-wire or four-wire circuits usually represent each signal as two different pulse lengths (e.g., 150
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the disposition of the routing of the telephone call attempt (e.g., called-party's telephone is currently busy, called-party's telephone is now ringing, called-party's telephone is out of service)
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R2 signaling specifications were first published by the
International Telegraph and Telephone Consultative Committee (CCITT) in ITU White Book Volume VI of 1969, and are maintained by the
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R2 signalling refers to a vast number of variants of R2 that resemble each other to varying degrees. For most R2 variants, each such variant of R2 is promulgated by the
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of each nation and/or by a telecommunications equipment manufacturer who addressed that national market with a nation-specific adaptation of one of their products.
358:. This allowed interconnection, interoperability and communication between a more diverse range of equipment types and telecommunication administrations.
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adopted more readily around the world than the proprietary standards of Bell System and
Western Electric. As a result, R2 has even found sparse use in
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Later in the 20th century, use of R2 signalling spread beyond Europe to all regions of the globe, including Mexico on the North
American continent.
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competitive market, tendering for business from
European PTTs. A more open set of technical standards developed, particularly under the auspices of
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electrical pulses also could be represented in digital form by a signalling DS0 channel in the trunk, which is normally channel 16 in an E1 trunk.
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A signalling protocol may be visualized by two contexts: the information it conveys, and the location of participants in the network.
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All R2 register signalling variants use a combination of two frequencies of audio signals. Each pair of frequencies is called a
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the calling party's category (e.g., normal subscriber, high-priority subscriber, operator, coin-operated telephone)
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versus 600 milliseconds), where the two different meanings of those two different pulse lengths varies by context.
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message, whereas the incoming register's pull signals, which request information from the outgoing register, are
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uses in-band multifrequency signals to transfer calling-party and called-party addressing information.
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is the direction from the dialling telephone's switch to the called telephone's switch, and
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IVth
Plenary Assembly (Mar Del Plata, 23 September-25 October 1968), White Book Volume VI,
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terms, the outgoing register's first push signal to the incoming register is similar to a
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the digits 11 through 14 for special-service requests (e.g., route to operator, add
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group comprises supervisory signals for call setup and termination, while inter
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without explicit intervening requests from the calling-party's switch.
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the digits 1 through 10 of the destination telephone number (termed
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R2 line signalling variants that support R2 line signalling in its
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in the 1970s and then later by ITU-T with only modest evolution.
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the digits 1 through 10 of the origin telephone number (termed
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Each R2 national variant conveys at least the following.
39:(ITU-T) in Recommendations Q.400 through Q.490. The name
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R2 signaling methods may be logically divided into two
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402:- Specifications of Signalling System R2
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43:is a derived from a designation as
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413:Telephone Signaling and Switching
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400:ITU-T Recommendation Q.400-Q.490
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453:Signaling (telecommunications)
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81:is the inverse direction:
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519:Multi-frequency signaling
514:Dual-tone multi-frequency
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337:multi-frequency signaling
494:Special information tone
534:Signalling System No. 7
529:Signalling System No. 6
524:Signaling System No. 5
339:(MF) practiced in the
231:two-wire or four-wire
552:Telephones portal
333:Regional System No. 1
329:Regional System No. 2
327:R2 is a mnemonic for
136:calling-party address
66:Signaling information
45:Regional System No. 2
380:Compelled signalling
298:Multifrequency tones
120:called-party address
98:acquisition (termed
17:Signalling System R2
277:Signalling variants
243:Register signalling
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21:signalling protocol
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60:register signaling
25:telecommunications
571:Telephony signals
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484:Reorder tone
474:Ringing tone
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323:Nomenclature
313:peer-to-peer
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54:groups. The
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479:Busy signal
341:Bell System
215:signalling
202:signalling
186:signalling
175:signalling
163:signalling
147:signalling
131:signalling
115:signalling
95:signalling
387:References
354:and later
464:Dial tone
309:proleptic
257:Standards
248:generate
211:backward
565:Category
504:Zip tone
469:Ringtone
374:See also
213:register
173:register
171:forward
161:register
159:forward
145:register
143:forward
129:register
127:forward
113:register
111:forward
106:channel
79:backward
52:protocol
509:2600 Hz
291:digital
233:circuit
100:seizure
75:Forward
364:Canada
237:analog
19:is a
356:ETSI
352:CEPT
271:CEPT
200:line
184:line
93:line
23:for
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263:PTT
104:DS0
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41:R2
445:e
438:t
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