ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å°6Ø'°6Ø'Å ÐÓÓÃÃRecommendation K.24ÄÄ Áà/ÁMETHOD FOR MEASURING RADIO FREQUENCYƒ Áà-ÁINDUCED NOISE ON TELECOMMUNICATIONS PAIRSƒ 1.ÁHÁÃÃPurpose of this RecommendationÄÄ Ð X ÐÁHÁThis Recommendation is intended to standardize the method for measuring radio frequency induced noise that may cause degradation of equipment performance and transmission quality. Standardization of the method for measuring induced noise makes possible the international standardization of the quality of the telecommunication system. 2.ÁHÁÃÃScopeÄÄ ÁHÁThis Recommendation considers measurement methods for radio frequency induced noise at any telecommunication pair. Locations for measurement are both the cable entry point into a building and the interface point of a terminal equipment. ÁHÁThe frequency range to be considered is 10 kHz to 30 MHz. ÃÃNoteÄÄ © Above 30 MHz, the technical problems of making measurements have not been solved and are therefore still under study. 3.ÁHÁÃÃCircuits for measuring radio frequency induced noise voltageÄÄ ÁHÁ1)Á   ÁMeasured mode of induced noise voltage ÁHÁBoth transverse and longitudinal voltages should be measured. ÁHÁ2)Á   ÁMeasured condition of telecommunication line ÁHÁMeasurements should be made with all telecommunications equipment ÁI°"JÁdisconnected at measuring end and with a measurement termination Á:¨;Ánetwork. ÁHÁi)Âh   ÂTermination network for measurementsÆÆ ÁHÁÂX  ÂMeasurements should be made at both the cable entry point into the subscribers premises and at the terminal equipment point. In the measurement, a T network shown in Figure 1 should be used. The longitudinal conversion loss of the T network should be at least 10 dB higher than the value of the LCL for the cable type to be measured (e.g., 60 dB cable requires 70 dB measurement termination network).ÆÆ ÃÃNoteÄÄ © Values of Rx and Ry are under consideration. Administrations and RPOAs are requested to make measurements at both sets of values indicated in Figure 1. ÁHÁii)Âð   ÂReference earthing pointÆÆ ÁHÁÂX  ÂEither of two reference earthing points may be used. In order of preference they are: 1) the screen of the cable or 2) the primary protection ground terminal, protective earth, or nearby grounded metal work. Since it affects the result, the reference earthing point used for a measurement should be stated.ÆÆ ÃÃNoteÄÄ © For transverse measurements, a connection to a reference point may not be required, but care must be taken with the capacitance of the measurement equipment to ground. This may be done by using battery powered measuring equipment. An isolating transformer for mains powered equipment, or a balun termination network, must be used when measuring metallic transverse voltage. ÂHHÂÂX  ÂÁ€ HÁÁ€ÁÁHÁiii)Á øÁTermination Network to use at the central officeÆÆ Ð H ÐÂHHÂÂX  ÂOn inside house wire (such as the S/T interface line of ISDN) it is important to terminate the far end of the cable. However, when measuring at the entry point of the local network into the customer's premises (such as the two©wire interface to NT1 of ISDN), it is not important to have a termination at the far end if the cable lengths exceeds 1 km. Below 1 km, it may still be possible to make measurements without terminating the far end, depending on the frequency of the interfering signal and the make©up of the local network.ÆÆ Ð ` Ð ÁHÁ3)Á   ÁDetector type Ð ( ÐÂHHÂThe detector shall have fundamental characteristics as defined in Section 1 of CISPR specification for radio interference measuring apparatus and measurement method, CISPR 16, 1987.ÆÆ Ð ` Ð ÁHÁ4)Á   ÁBandwidth of measurement Ð Ð ÐÂHHÂThe bandwidth of measurement shall have fundamental characteristics as defined in Section 1 of CISPR specification for radio interference measuring apparatus and measurement method, CISPR 16, 1987.ÆÆ Ð ` Ð Ð ° ÐÂHHÂImprovements in narrowing the bandwidth and the standardization of appropriate measuring equipment needs further study in cooperation with CISPR.ÆÆ Ð ` Ð ÁHÁ5)Á   ÁElectric field immunity of measurement equipment Ð H ÐÂHHÂThe test equipment should have an overall immunity to electromagnetic fields in accordance with CISPR publication 16. Adequate accuracy should be provided for extending the use of the equipment to locations with field strengths above 3 V/M to 10 V/M.ÆÆ Ð ` Ð