1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 4 G0BISTELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU4%2-).!,G0G0%15)0-%.4G0G0!.$G0G002/4/#/,3G0G0 amended at Geneva, 1972, 1976 and 1980)1 Type of circuits to be usedSince circuits of the general telephone network and the station lines of telephone subscr
2、ibers should be capableof being used for document facsimile transmissions on the general network, the circuits to be used are those of thegeneral switched network which have 2-wire terminals at both ends of the facsimile station.Note For the actual document transmission, which is one-way, there is n
3、o need to cater for the disabling ofecho suppressors. Compandors do not seem detrimental to document facsimile transmission.2 Overall lossThe conditions for overall transmission loss are the same as those for circuits of the general switched telephonenetwork.3 ModulationEquipment conforming to Recom
4、mendation T.2 or Recommendation T.3 may be used. In the case ofRecommendation T.2 equipment, frequency modulation shall be used.4 PowerIn order to avoid the risk that facsimile signals be disturbed, e.g. by dial pulses transmitted over adjacentchannels or by noise, it is important that the sending l
5、evel should be as high as possible, provided, however, that it shallnot exceed 13 dBm0 on the trunk circuit for frequency-modulation equipment conforming to Recommendation T.2 orthat the mean power in any hour, in one direction of transmission, shall not exceed 32 microwatts ( 15 dBm0) at thezero re
6、lative level point of the trunk circuit for equipment conforming to Recommendation T.3.The maximum power output of the transmitting apparatus into the line shall not exceed 1 mW whatever thefrequency.5 Amplitude and phase distortionEquipment conforming to Recommendation T.2 should not require any special treatment. However, equipmentconforming to Recommendation T.3 may require both amplitude and phase distortion correction on certainconnections.
