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)#%53%2G0G0#/.42/,G0G0/ in fact, thisRecommendation has been set up to be as service-independent as possible.2 In stati
2、ng and recommending user procedures it is important to have global information about terminalcapabilities. This Recommendation, however, is drafted as terminal-independent as possible. It contains fundamentalprinciples of user interfaces as far as these are relevant to user access to the ISDN, and d
3、oes not specify terminalrequirements.The CCITT,considering(a) that the ISDN will make available new services for customers and Administrations;(b) t the changeover from the present networks to the ISDN will be gradual;(c) that, from a users point of view, private networks and public networks offer s
4、ome similar services and alsoservices that one or the other does not provide;(d) that certain services have specific user procedures and their own methods of presenting information to theuser;(e) that users may benefit from uniformity in user procedures for selecting a service and for starting, swit
5、chingbetween, and ending communications;(f) that information from the telecommunication system to the user can be sent in the form of tones, verbalannouncements, or visual indications on a display;(g) that the use of terminals containing a visual display is becoming more and more common intelecommun
6、ication applications;(h) that the ISDN offer users the possibility of handling two or more connections simultaneously;(i) that handling connections simultaneously may be difficult for the user;(j) that information presentation to the user should be based on human factors considerations;(k) that term
7、inals may be distinguishable into dedicated (service-specific) terminals and terminals with whichseveral teleservices can be offered,recommends(1) that the methods with which communication sessions are selected, started, switched between each other andended, should, where appropriate, make allowance
8、 for different levels of user experience;(2) that, when a similar capability using similar terminals is offered through a private network and a publicnetwork, user procedures should be similar;2 Fascicle II.2 - Rec. E.330(3) that, where a terminal supports “higher level”1)procedures and has the same
9、 function keys used for lower-level procedures in other terminals, then these lower-level procedures should still be operable, to achieve thefunctionality reached by higher-level procedures.(4) that, on more advanced telecommunication terminals, however, other input mechanisms, having similarfunctio
10、ns to those controlled by the function keys mentioned in (3), may replace these function keys;(5) that, for voice and non-voice services, procedures should be similar for analogous supplementary serviceswhen terminals with similar capabilities are used;(6) that tones, verbal announcements and visual
11、 indications, which are used in the existing networks should notbe changed in the ISDN as long as their functions remain the same;2).(7) that ending a communication session can be accomplished from either end, except for emergency services;(8) that it is preferred to give information to users at eit
12、her end of a communication path by means of anauditory or visual indication when the communication is on hold;3)(9) that in those cases where starting or switching between communication sessions is not possible or mayresult in a deterioration of the existing communication session(s), appropriate aud
13、itory or visual indication should begiven to the user;(10) that when two or more communication sessions are handled at the same time on the sametelecommunication terminal and the user uses a stop procedure valid for all communication sessions, it is preferred togive the user the opportunity to selec
14、t which session or sessions are to be terminated._1)“Higher level” and “lower level” refer here to the degree to which the capabilities of a terminal facilitate its use. For example, aterminal with only digits and a star and a square (see Recommendation E.161) may be able to achieve the same functio
15、nsthrough lower-level procedures as a better equipped terminal with, for example, dedicated function buttons, in addition to itsdial, where higher-level, more convenient procedures could be used.2)See Recommendation E.184.3)Further study is required to determine whether or not a communication session which was put on hold becomes active as soonas the present communication session is ended by the user and, if so, whether this is the communication session which was puton hold first or last. This subject should also be dealt with in the next study period.
