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ITU-T E.131 Document Information:
Title
Subscriber Control Procedures for Supplementary Telephone Services
International Telecommunication Union/ITU Telcommunication Sector
Publication Date:
Jan 1, 1993
Scope:
General
Many Administrations are planning to introduce supplementary
telephone services which are likely to be viable only if controlled
by the user (a list of possible supplementary telephone services is
given in Supplement No. 1 at the end of this fascicle). It is
therefore necessary to consider means of providing users with
procedures by which such control can be achieved. The purpose of
this Recommendation is to prevent an undesirable proliferation, in
various countries, of subscriber control procedures for such
services. Descriptions are given below of three control procedures
schemes now in use or in various stages of evolution. Guidelines
are offered to Administrations planning to offer subscriber
controlled supplementary services. Reference is made to Annex A for
a glossary of terms used in this Recommendation.
It is recognized that not all aspects of all supplementary
services will affect the international telephone service, but a
degree of international coordination is considered necessary
because:
a) the same or similar supplementary services will exist on
national and international networks; it is desirable to have
similar control procedures for both applications;
b) a supplementary service which is only national now may be
international in the future; in that case changes in control
procedures might be impossible or expensive;
c) subscribers who travel or move will be less inconvenienced if
control procedures for supplementary services do not change from
one country to another;
d) compatibility between control procedures for telephone
services and simple parallel end-to-end data transmission is highly
desirable, because the same telephone instrument is used in both
cases;
e) standardized control procedures make possible lower equipment
and customer instruction costs.
Access to individual services requires that the supplementary
service numbering plan have a sufficient capacity to meet all
reasonable future needs; control of the services requires the
ability to define functional requirements to the system.
The introduction of push-button telephones providing 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 most subscribers, only two
additional non-numerical signals will be available for control
purposes. Study therefore has been directed towards evolving
schemes for control procedures which are acceptable both from the
human factors and technical aspects and do not require more than
two non-numerical signals.
The same push-button telephone set that is used in dedicated
telephone networks may be used as a subscriber instrument in
service integrated networks. It is desirable that in this case the
control procedures for a given supplementary telephone service
still apply.
Where the normal 12-button telephone set is also used for
services other than telephony, e.g. for data, videotelephone, etc.,
the control procedures used for these services should be compatible
with the control procedures used for supplementary telephone
services.
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