1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 * TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%,%6)3)/.G0G0!.$G0G03/5.$G0G042!.3-)33)/.(90/4(%4)#!,G0G02% amended at Geneva, 1976, and at Melbourne, 1988)Terrestrial systems and systems in the fixed-satellite serviceThe CCITT,considering(a) that there i
2、s a need to define a hypothetical reference circuit to enable design performance standards to beset;(b) that the hypothetical reference circuit should allow the different types of sound-programme circuits to becompared on a common basis,unanimously recommends(1) that the main features of the hypothe
3、tical reference circuit for sound-programme transmissions over aterrestrial system (shown in a Figure 1/J.11), which may be provided by either radio or cable, should be: the overall length between audio points (B and C) is 2500 km, two intermediate audio points (M and M) which divide the circuit int
4、o three sections of equal lengths, the three sections which are lined up individually and then inter-connected without any form of overalladjustment or correction;(2) that the main features of the hypothetical reference circuit for sound-programme transmissions over asystem in the fixed-satellite se
5、rvice (shown in Figure 2/J.11) should be: one link: earth station satellite earth station, one pair of modulation and demodulation equipments for translation from baseband to radio frequency, andfrom radio frequency to baseband, respectively._1)This Recommendation corresponds to CCIR Recommendation
6、502.2)The hypothetical reference circuits defined in this Recommendation should apply for both analogue and digital systems.3)For maintenance purposes there may be a need to define other circuits of which an illustration is shown in Annex A of thisRecommendation.2 Fascicle III.6 - Rec. J.11ANNEX A(t
7、o Recommendation J.11)Illustration of an international sound-programme connectionFigure A-1/J.11 illustrates a typical international sound-programme connection in which: point A, to be considered as the sending end of the international sound-programme connection, may be thepoint at which the program
8、me originates (studio or outside location); point D, to be considered as the receiving end of the international sound-programme connection, may be aprogramme-mixing or recording centre or a broadcasting station; the local sound-programme circuit AB connects point A to the sending terminal station, p
9、oint B, of theinternational sound-programme circuit BC; the local sound-programme circuit CD connects point C, the receiving terminal station of the internationalsound-programme circuit BC to the point D.The hypothetical reference circuit must not be considered identical to any of the sound-programm
10、e circuitsillustrated above or to those defined for maintenance purposes in 1. However, some of these circuits may display thesame structure as the hypothetical reference circuit. Such types of circuits are: an international sound-programme connection comprising three audio sections; a single sound-
11、programme circuit made up of three audio sections.In this case, the performance standards set for the hypothetical reference circuit may be applied to thesecircuits.Fascicle III.6 - Rec. J.11 3Reference1 Maintenance; international sound-programme and television transmission circuits. Recommendations of theN Series. Fascicle IV.3.
