ITU-T I 241 7-1993 TELEPHONY 7 KHZ TELESERVICE《7 KHz远程服务电话》.pdf
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1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF IT INTEGRATED SERVICES DIGITAL NETWORK (ISDN) SERVICE CAPABILITIES TELESERVICES SUPPORTED BY AN ISDN 1.241.7 (03193) TELEPHONY 7 kHz TELESERVICE ITU-T Recommendation 1.241.7 (Previously “CCIlT Recommendation”) CC
2、ITT RECMN*I.Z4L. 7 93 48b259L 0580547 237 FOREWORD The ITU Telecommunication Standardization Sector (IT-T) is a permanent organ of the International Telecom- munication Union. The IT-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a vi
3、ew to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. IT-T Recommendation 1.24
4、1.7 was prepared by the IT-T Study Group I (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the Intemational Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the IT Telecommunicati
5、on Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the text to references containing the a
6、cronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new U structure. 2 telecommunication administration and a recognized operating agency. In this Recommendati
7、on, the expression “Adminisiration” is used for conciseness to indicate both a Ail rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, witbout permission in writing from the ITU. CCITT
8、 RECMN+I.243 . 7 93 m 4862593 0580548 I175 m CONTENTS FOREWORD Definition Description 2.1 General description . 2.2 Specific terminology . Procedures . 3.1 Provision and withdrawal 3.2 Normal procedures 3.3 Exceptional procedures . Charging capabilities . Interworking requirements . AtmbuteNalues .
9、6.1 Low layer attributes . 6.2 Access attributes . 6.3 High layer attributes 6.4 General attributes Page 3 3 1 1 1 2 2 2 3 4 4 4 4 4 5 5 Recommendation 1.241.7 (03/93) i CCITT RECMNrI.241. 7 93 4862592 0580549 002 Recommendation 1.241.7 TELEPHONY 7 kHz TELESERVICE (Helsinki, 1993) 1 Definition The t
10、elephony 7 kHz teleservice for an ISDN interface is a symmetrical, bi-directional real time teleservice which allows users to interchange high quality speech or sounds using the circuit-mode 64 kbit/s 8 kHz structured multi-use bearer service category. 2 Description 2.1 General description The telep
11、hony 7 IrHz teleservice is defined as a fully standardized ISDN teleservice following the principles given in Recommendation 1.210. The telephony 7 IrHz teleservice enables a user to communicate with high quality speech or by interchanging sounds with higher quality than that provided by 3.1 kHz tel
12、ephony. The communication is bi-directional, with both directions continuously and simultaneously active during the speech phase, with a frequency range from 50 to 7000 Hz. User information is transferred over the B-channel, signalling is provided over the D-channel. Tones and announcements are prov
13、ided by the network using B-channel coding in Recommendation G.711. It is possible to use 7 kHz terminals to communicate with other ISDN telephone or videophone terminals. A 7 kHz terminal is capable of supporting 3.1 kHz telephony. It is also possible to use 7 MIZ terminals to communicate with term
14、inals connected to the PSTN. Fail-back procedures whereby a calling user can communicate with a called user having a 3.1 kHz terminal, or with users on the PSTN, are as described in Recommendation 1.231.9. The telephony 7 kHz teleservice allows the communication between - - two user (e.g. terminals)
15、 in a point-to-point configuration via the ISDN over a B-channel; three or more users in a multipoint configuration as invoked by some supplementary services. The maximum delay for the user information is the same as it is specified for the general telephone network (400 ms). 2.2 Specific terminolog
16、y For the purposes of this Recommendation, the following definitions apply. 7 kHz terminal: A terminai that supports the telephony 7 IrHz teleservice. 3.1 kHz terminal: A terminal that supports 3.1 kHz telephony. Videophone terminal: A terminal that supports videotelephony. fall-back: A mechanism pe
17、rformed either by the network or by the calling terminal that allows 7 ICHZ terminals to establish calls to 3.1 kHz terminals. retention timer: This timer specifies the amount of time that the network retains the call information of the original call upon encountering busy or being released. This ti
18、mer is a network provider option. The value for this timer is greater than 15 seconds. Recommendation 1.241.7 (03/93) I CCITT RECflN*I*Z9L* 7 93 = 9862591 0580550 823 = Subscription option Maximum number of information channels available at the called user Maximum number of total calls present at th
19、e called user 3 Procedures Value - m, with m is not greater than the number of information channels on the interface - n, with n is not greater than the number of information channels on the interface 3.1 Provision and withdrawal 3.1.1 The telephony 7 kHz teleservice may be provided after prior arra
20、ngement with the service provider. 3.1.2 As a service provider option, the telephony 7 IrHz teleservice can be offered with several subscription options which apply separately to each ISDN number, ail or group of ISDN numbers on the interface. For each subscription option, only one value can be sele
21、cted. Subscription options for the interface are summarized below: The called user can be an ISDN number or group of ISDN numbers on the interface. NOTE - More than one ISDN number cau be associated with the servicehnterface as a part of a supplementq service such as the Multiple Subscriber Number s
22、upplementary service. In case of one ISDN number, the option given above for the number of calls can only exceed the number of information channels in association with a supplementary service (e.g. the Call Waiting supplementary service). As a network provider option, separate values may be specifie
23、d for incoming and for outgoing calls for either or both of the limits. 3.2 Normal procedures Ail user-network signalling is over the D-channel. 3.2.1 Originating the call (call set-up) The telephony 7 kHz teleservice is originated by the originating user activating the terminal, performing the serv
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