1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 . TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#%G0G0/&G0G0).4%2.!4)/.!,3/5.$G0G13G002/2!-%G0G0!.$G0G04%,%6)3)/.42!.3-)33)/.G0G0#)2#5)43-!8)-5-G0G00%2-)33)“,%G0G00/7%2$52).G0G0!.G0G0).4%2.!4)/.!,3/5.$G0G13G002/2!-%G0G042!.3-)33)/.)45G134G0G0Recom
2、mendationG0G0. (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation N.15 was published in Fascicle IV.3 of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are i
3、dentical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part o
4、f this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle IV.3 - Rec. N.15 1Recommendation N.15Fascicle IV.3 - Rec. N.15MAXIMUM PERMISSIBLE POWER DURING AN INTERNATI
5、ONALSOUND-PROGRAMME TRANSMISSIONGeneralTo check that the maximum power transmitted during a sound-programme transmission does not exceed thelimits allowed by Administrations, it is recommended that broadcasting organizations and the terminal ISPCs of theinternational sound-programme connection shoul
6、d use volume-meters or peak programme meters, the same type ofmeter being used for preference by both the telephone Administration and the broadcasting organization of a country.Since the international sound-programme connection is accurately adjusted before it is made available to thebroadcasting o
7、rganizations, there will be no danger of overloading the amplifiers during the sound-programmetransmission if care is taken not to exceed the permissible limit at the sending end of the international sound-programmeconnection.Hence, this check can be done only by the broadcasting organization and th
8、e ISPC of the transmitting country,and a check made further down the line would not seem to be very effective.If so desired, monitoring equipment (volume-meters, peak-indicators) can be connected at the receiving end ofthe international sound-programme link and of the international sound-programme c
9、onnection to obtain informationabout the general nature of the transmission. In this case, monitoring equipment at the two locations in the incomingcountry will have to be of the same type, but there is no need for the same kind of monitoring equipment to be used inboth outgoing country and incoming
10、 country.1 Maximum level permitted on sound-programme circuitsThe peak power permitted on a sound-programme circuit should not exceed +9 dBm at a point of zero relativelevel on the sound-programme circuit.(This corresponds to a peak voltage of 3.1 volts when measured as a 600-ohm through-level at a
11、zero throughrelative level point. The r.m.s. value of the sinusoidal signal with this peak value is 2.2 volts).If a transmission system overload is identified as being due to sound-programme transmission on 6.4 kHz or10 kHz sound-programme circuits, the level at the zero relative point should be red
12、uced by 3 dB to achieve anaccompanying reduction in peak power, in accordance with Recommendation J.22, A.2 1.2 Maximum level permitted on an international telephone circuit used to carry a sound-programmetransmissionThe power permitted on the international telephone circuit carrying a sound-program
13、me transmission shouldnot exceed +3 dBm at a point of zero relative level on the international telephone circuit. To allow the +9 dBm0 peaklevel permitted on a sound-programme circuit a 6 dB loss should be introduced at a point before the internationaltelephone circuit enters a carrier system. At th
14、e receiving side a corresponding amplification of 6 dB at the end of thetelephone circuit should be provided.This reduction is necessary to avoid overloading on the carriers system. Reasons for the possible overload are:a) Commentary circuits are used in one direction only in comparison to a normal
15、telephone connection. Thisleads to an increase of the mean power level.b) In most cases the broadcasting authorities use better quality microphones compared with normaltelephone sets.Experience has shown that an attenuation of 6 dB is the most suitable value for this purpose.Reference1 CCITT Recommendation Performance characteristics of 10 kHz type sound-programme circuits, Red Book,Vol. III, Rec. J.22, ITU, Geneva, 1984.
