1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 4 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%2-).!,G0G0%15)0-%.4G0G0!.$G0G002/4/#/,3G0G0 amended at Mar del Plata, 1968;at Geneva, 1972, 1976 and 1980)1 Type of circuits to be usedThe telephone-type circuits used should have characteristics as recomme
2、nded in Recommendation H.12.Note If the leased circuit is used alternately for telephone conversation and facsimile transmission and if thelatter is unidirectional, it is not necessary to provide for disabling echo suppressors located on the long-distance leasedcircuit. However, when such a circuit
3、is used for the simultaneous operation in both directions appropriate measuresshould be taken to disable echo suppressors before the actual facsimile transmission takes place.2 ModulationEquipment conforming to Recommendation T.2 or Recommendation T.3 may be used. In the case ofRecommendation T.2 eq
4、uipment, either amplitude or frequency modulation may be chosen.3 PowerThe maximum power output of the transmitting apparatus into the line shall not exceed 1 mW whatever thefrequency.For frequency-modulation equipment conforming to Recommendation T.2, the level at the transmitter outputshall be so
5、adjusted that the level of the facsimile and control signals on the trunk circuit does not exceed 13 dBm0regardless of the type of operation (duplex or simplex).For amplitude-modulation equipment conforming to Recommendation T.2, higher black levels may be usedprovided the mean power in any hour, in
6、 one direction of transmission, does not exceed 32 microwatts (15 dBm0) atthe zero relative level point of the trunk circuit.For equipment conforming to Recommendation T.3, higher white levels may be used provided the mean powerin any hour, in one direction of transmission, does not exceed 32 microw
7、atts (15 dBm0) at the zero relative level pointof the trunk circuit.4 Multipoint transmissionIf facsimile transmissions take place simultaneously from a transmitting station to several receiving stations,arrangements shall be made at the junction points so that, on the circuits following the junctio
8、n points, the same powerlevels are maintained as those prescribed for individual transmissions.5 Phase distortionEquipment conforming to Recommendation T.2 should not require any special treatment. However, equipmentconforming to Recommendation T.3 may require phase distortion correction in some cases.
