1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 % TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%0(/.%G0G0.%47/2+G0G0!.$G0G0)3$./0%2!4)/. G0G0.5-“%2). G0G02/54).!.$G0G0-/“),%G0G03%26)#%35“3#2)“%2G0G0#/.42/,G0G002/#%$52%3G0G0 it is desirableto have similar control procedures for both applications;b) a
2、 supplementary service which is only national now may be international in the future; in that case changesin control procedures might be impossible or expensive;c) subscribers who travel or move will be less inconvenienced if control procedures for supplementaryservices do not change from one countr
3、y to another;d) compatibility between control procedures for telephone services and simple parallel end-to-end datatransmission is highly desirable, because the same telephone instrument is used in both cases;e) standardized control procedures make possible lower equipment and customer instruction c
4、osts.1.3 Access to individual services requires that the supplementary service numbering plan have a sufficient capacityto meet all reasonable future needs; control of the services requires the ability to define functional requirements to thesystem.The introduction of push-button telephones providin
5、g signals in addition to the normal decimal range (0-9)offers a means of providing the necessary function signals. Since the 12-button instrument is likely to be used by mostsubscribers, only two additional non-numerical signals will be available for control purposes. Study therefore has beendirecte
6、d towards evolving schemes for control procedures which are acceptable both from the human factors andtechnical aspects and do not require more than two non-numerical signals.1.4 The same push-button telephone set that is used in dedicated telephone networks may be used as a subscriberinstrument in
7、service integrated networks. It is desirable that in this case the control procedures for a givensupplementary telephone service still apply.Where the normal 12-button telephone set is also used for services other than telephony, e.g. for data, video-telephone, etc., the control procedures used for
8、these services should be compatible with the control procedures usedfor supplementary telephone services.2 Schemes for control proceduresRecognizing that: the CCITT has not as yet recommended a unique scheme of subscriber control procedures forsupplementary telephone services; the CCITT is still stu
9、dying such control procedures; further proliferation of schemes is undesirable because this would result in subscriber confusion, lessefficient use of the telephone network and might make it more difficult to work towards an optimumscheme;it is recommended that:2 Fascicle II.2 - Rec. E.131 Administr
10、ations contemplating the introduction of services which require new control procedures joinactively with the ongoing study; Administrations wishing to adopt a scheme of subscriber control procedures should apply one of thosedetailed below to the maximum extent feasible rather than establish a new sc
11、heme.3 Description and analysis of code schemes for supplementary telephone services3.1 General3.1.1 Three code schemes for supplementary telephone services, currently in use or under study will be brieflydescribed and analyzed. They are:1) AT2) CEPT code scheme (Europe);3) NTT code scheme (Japan).3
12、.1.2 It is intended that Recommendation E.131 should be reviewed when experience of the three code schemes isavailable. It may then be possible to determine if one of them, or perhaps a fourth which incorporates the best featuresof all three, is to be prefered.3.1.3 These schemes are still evolving
13、and are liable to changes in details as study progresses or experience is gained.The information presented is an outline only and presents the position at a point in time when the Recommendation ispublished. Administrations considering the implementation of supplementary services requiring control p
14、roceduresshould approach the appropriate Administration or authority to seek detailed and up-to-date information.3.2 Description of the code schemes3.2.1 The information sent by the subscriber to the exchange for the control of a service is made up of a number ofbasic functional elements, some or al
15、l of which may appear explicitly in a particular message. These basic functionalelements are (see the glossary in Annex A):1) mode or type of communication identification,2) access to supplementary services,3) service identification,4) function identification,5) supplementary information,6) block se
16、paration,7) message suffix.3.2.2 The mode or type of communication identification element is unlikely to be used for telephone services andallocation of codes for this purpose within these schemes is tentative. This element is therefore excluded fromconsideration for the present.3.2.3 The main diffe
17、rences between the three code schemes are in the methods used to encode the various functionalelements and the order in which they must be presented. In all code schemes a separate code is used for the dialling ofabbreviated numbers.3.2.4 For each of the three code schemes, Table 1/E.131 gives the f
18、ormat of the information sent by the subscriber tothe exchange:i) without supplementary information,ii) with one block of supplementary information,iii) for the dialling of abbreviated numbers.Fascicle II.2 - Rec. E.131 3In the Table 1/E.131, the digits below each message identify the functional ele
19、ments as listed in 3.2.1 above.TABLE 1/E.131ATSI = supplementary information;SDT = second dial tone;(.) = not always used. For detailed explanations, see 3.2.5 below;*= “star” button of telephone set as defined in Recommendation E.161;# = “square” button of telephone set as defined in Recommendation
20、 E.161.3.2.5 In the three code schemes the basic functional elements are realized in the following way:Access to supplementary services (element 2)ATservice code prefix #: deactivation and erasure.NTT: a numerical function code that is only required for certain services. (If a function code is neede
21、d, thesubscriber is informed by means of a dial tone).0 = deactivation,1 = activation,2 = registration.Block separation (element 6)AT however, if in this case the subscriber dials a blockseparator after the service code, the exchange should accept the message.NTT: the block separator *may be used be
22、tween the function code and the first block of supplementary information, and between successive blocks of supplementary information for push-button telephonesonly.Message suffix (element 7)AT*N(N) abbreviated numbers: 0-9 or 00-99 available.NTT: abbreviated numbers: 00-99 available.3.3 Features of
23、each of the code schemesThe features of each of the code schemes compared with one or both of the other two are given below.3.3.1 AT&T code scheme1) The *symbol is used for access to supplementary services.Fascicle II.2 - Rec. E.131 52) Control procedures from rotary dial and push-button telephones
24、are compatible.3) The messages sent by the subscriber to the exchange are short.4) Some two-digit codes have been reserved so as to permit three- digit (or longer) service codes to beintroduced in the future without changes in the existing service codes.5) The message suffix is not essential.6) One,
25、 two and more digit abbreviated numbers are possible without the need to use different initial digits.3.3.2 CEPT code scheme1) When only prefixes are used, the telephone numbering plan is not influenced by the code scheme forsupplementary services.2) When only prefixes are used, exchange logic is si
26、mplified.3) When only prefixes are used, the use of similar control procedures in PABXs and the public network isfacilitated.4) The abbreviated dialling numbering plan is divorced from the service code numbering plan and does notimpose restrictions on it.5) The service code remains the same irrespec
27、tive of the function required.6) Each important function is defined by a unique prefix.7) Other prefixes are available for new service functions.8) A mandatory message suffix avoids the need for time-out, fixed message length or complex programming.9) When the message suffix method for abbreviated d
28、ialling is used, one, two and more digit abbreviatednumbers are possible without the need to use different initial digits.3.3.3 NTT code scheme1) The use of a prefix simplifies exchange logic.2) The use of a prefix facilitates the use of similar control procedures in PABXs and the public network.3)
29、Other prefixes are available for future use.4) A measure of compatibility between the control procedures from rotary dial and push-button telephones ispossible.5) The abbreviated dialling numbering plan is divorced from the service code numbering plan and does notimpose restrictions on it.6) The ser
30、vice code remains the same irrespective of the function required.7) Each important function is defined by a unique function code.8) Ten function codes are available.9) Allocating a function code after a service code makes it possible to separate basic switching functions fromsupplementary service pr
31、ocessing functions. This facilitates the application of new services to an existingold-type exchange.10) The control procedures are similar to the control procedures in the NTT end-to-end communicationservices.11) The function code can be deleted if not required.6 Fascicle II.2 - Rec. E.131ANNEX A(t
32、o Recommendation E.131)Glossary of termsThis glossary gives the meanings currently allocated to various terms to facilitate the study and evaluation ofcontrol procedures. They are subject to review as the code schemes evolve.A.1 supplementary telephone serviceF: service tlphonique supplmentaireS: se
33、rvicio telefnico suplementarioAny service provided by the telephone network in addition to the fundamental telephone service.A.2 control procedureF: procdure de commandeS: procedimiento de controlA method in which information is exchanged in a predetermined forward order and backward order betweensu
34、bscriber and exchange to effect control of a service.A.3 commandF: commandeS: instruccin (de control)A single specific manipulation at the subscriber set causing transmission of a signal which specifically indicatesthe manipulation to the exchange. For certain control procedures either one single co
35、mmand or a succession ofcommands are required.A.4 characterF: caractreS: carcterA single specific symbol, number or letter used to designate the diallable signal caused by a command.A.5 messageF: messageS: mensajeA defined entity of information from the subscriber to the exchange pertaining to a cal
36、l or a control operationfor a service sent in one sequence over the signalling medium. A message may consist of one or more characterstransmitted in one or more blocks.A.6 codeF: codeS: cdigoOne character or a sequence of characters forming a part, or the whole, of a message with a specific meaning.
37、A.7 mode or type of communication identificationF: identification du type ou du mode de la communicationFascicle II.2 - Rec. E.131 7S: identificacin del tipo o del modo de la communicacinInformation used to give an instruction to the switching equipment to select the required network or mode ofcommu
38、nication, for example in the use of a multifunction terminal (video-telephone, 48 kbit/s wideband switched-network service, etc.).A.8 access to supplementary servicesF: accs aux services supplmentairesS: acceso a servicios suplementariosInformation used to instruct the switching equipment that the a
39、ssociated information relates to a supplementaryservice.A.9 service identificationF: identification de serviceS: identificacin de servicioInformation designating a supplementary service.A.10 function identificationF: identification de fonctionS: identificacin de funcinInformation indicating the type
40、 or types of process to be applied to the service.A.11 block separationF: sparation des blocsS: separacin de bloquesInformation indicating that the next character is the first character of a block of supplementary information.A.12 supplementary informationF: information supplmentaireS: informacin su
41、plementariaAny information, except the mode or type of communication identification, access to supplementary services,service identification, function identification, block separation and message suffix, which is required to be sent by thesubscriber to the exchange for the performance of a control o
42、peration. The supplementary information may consist ofone or more blocks.A.13 service codeF: code de serviceS: cdigo de servicioA numerical code designating a supplementary service.A.14 service code prefixF: prfixe de code de serviceS: prefijo de cdigo de servicioA non-numerical code preceding the s
43、ervice code and indicating the type or types of process to be applied tothe service.8 Fascicle II.2 - Rec. E.131A.15 function codeF: code de fonctionS: cdigo de funcinA code indicating the type or types of process to be applied to the service.A.16 block separatorF: sparateur de blocsS: separador de
44、bloquesThe character indicating that the next character is the first of a block of supplementary information.A.17 message suffixF: suffixe de messageS: sufijo de mensajeThe character indicating the end of the message.A.18 abbreviated numberF: numro abrgS: nmero abreviadoThe numerical code sent by a
45、caller using the Abbreviated Dialling Service which identifies the telephonenumber of the party to whom he wishes to be connected.A.19 abbreviated dialling prefixF: prfixe de numrotation abrgeS: prefijo de marcacin abreviadaThe non-numerical code indicating that the information following is an abbre
46、viated number.ANNEX B(to Recommendation E.131)During the Study Period 1977-80, an international laboratory experiment comparing subscriber performanceusing two of the recommended code schemes and a previous code scheme of AT&T, which was defined in Volume II.2of the Orange Book, was carried out unde
47、r the auspices of Working Party II/2 (Human Factors). The experiment wasconducted in five countries, Canada, Japan, Sweden, the United Kingdom and the United States of America. In theexperiment, a sample of subscribers were brought into the laboratory and asked to carry out a number of tasksinvolvin
48、g the use of three supplementary services. These tasks were carried out using a pushbutton telephoneconnected to a simulated telephone exchange. A different group of subscribers was tested using each of the codeschemes. Errors committed while carrying out the tasks and the time required to complete
49、them were recorded.The results of this experiment revealed that there are no large differences in subscriber performance using thethree code schemes. The experimental results did, however, reveal rather large differences among tasks. Those tasksthat required entry of supplementary information blocks produced higher error rates. This suggests that guidanceannoucements may be required to help subscribers at each step in complex control procedures. However, it should bepointed out that prior to carrying out the tasks only a brief explanation of the
