1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 / TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU30%#)&)#!4)/.3G0G0&/2G0G0-%!352).G0G0%15)0-%.40(!3%G0G0!.$G0G0!-0,)45$%G0G0()4G0G0#/5.4%23&/2G0G04%,%0(/.%G13490%G0G0#)2#5)43)45G134G0G0RecommendationG0G0/ (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommenda
2、tion O.95 was published in Fascicle IV.4 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 identical to the Blue Book version and copyright conditions remain u
3、nchanged (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 of this publication may be reproduced or utilized in any form or by
4、any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Fascicle IV.4 - Rec. O.95 1Recommendation O.95Fascicle IV.4 - Rec. O.95PHASE AND AMPLITUDE HIT COUNTERS FOR TELEPHONE-TYPE CIRCUITS(Geneva, 1980)1 GeneralThis specification provides t
5、he outline requirements for an instrument to be used for counting phase andamplitude hits on telephone-type circuits. The instrument will independently count the number of phase hits and thenumber of amplitude hits that occur in a given period of time.Phase or amplitude hits are defined as sudden po
6、sitive or negative changes in phase or amplitude of anobserved test signal which exceed a specified threshold and persist for a period of time greater than a specified duration.The specifications given below for the transmitter and receiver input section shall correspond with 2.2 b) to2.2 d) and 2.3
7、 b) to 2.3 d) of Recommendation O.91 in order to facilitate the combination of this instrument with aphase jitter meter conforming to Recommendation O.91 in one set.2 Transmitter2.1 Test signal frequency.1020 10 Hz2.2 Send level . 30 dBm to 0 dBm2.3 Output impedance (frequency range 300 Hz to 4 kHz)
8、 Balanced, earth free (other impedances optional) 600 ohms Return loss 30 dB Output signal balance 40 dB2.4 Phase jitter at source 0.1 degree peak-to-peak (see Recommendation O.91)3 Receiver input section3.1 Sensitivity and frequency rangeThe receiver should be capable of measuring with input levels
9、 between 40 and + 10 dBm and frequenciesbetween 990 and 1030 Hz.3.2 SelectivityPower line hum protection high-pass filter with a nominal cutoff frequency of 400 Hz with at least 12 dB peroctave slope.If the filter is not located directly at the instrument input, hum voltages equal to or smaller than
10、 the test signalshall not result in measurement errors greater than those with the filter in front of the set.Protection for limiter against channel noise low-pass filter with a nominal cutoff frequency of 1800 Hz withat least 24 dB per octave slope.3.3 Input impedance (frequency range 300 Hz to 4 k
11、Hz) Balanced, earth free Input longitudinal interference loss 46 dB3.3.1 Terminating impedance (other impedances optional) 600 ohms Return loss 30 dB3.3.2 High impedance approx. 20 kohms Bridging loss across 300 ohms 0.15 dB2 Fascicle IV.4 - Rec. O.954 Phase hit detection characteristics4.1 Threshol
12、d settingsSettings from 5 to 45 in steps of 5 shall be provided with an accuracy of 0.5, 10% referred to theselected threshold1). Additional settings may be optionally provided.4.2 Guard intervalA guard interval shall be provided by electronic gating or other equivalent means to prevent the counter
13、fromregistering phase hits shorter than 4 ms. The guard interval shall be tested as follows:With a threshold setting of 20, phase hits shall be counted correctly if the test signal is changed in phase by25 for a duration of 5 ms or more. When the duration of the 25 phase changes is gradually reduced
14、 until the phase hitcounter stops counting, the corresponding duration of the phase changes of the test signal shall be 4 ms 10%.4.3 Hit rate of changeSlow phase changes shall not be counted. This characteristic shall be tested as follows:With a threshold setting of 20, a phase hit shall be counted
15、when the phase of a test signal is linearly varied by100 in a time interval of 20 ms or less. A phase hit shall not be counted when the phase of the test signal is linearlyvaried by 100 in a time interval of 50 ms or more. The same requirements shall be met with 100 changes of oppositepolarity.4.4 A
16、mplitude of phase conversionAn 8 dB amplitude hit of either polarity shall not cause a phase hit to be counted at thresholds of 10 or more.5 Amplitude hit detection characteristics5.1 Threshold settingsSettings of 2, 3 and 6 dB shall be provided with an accuracy of 0.5 dB. Additional settings not ex
17、ceeding9 dB may be optionally provided.5.2 Guard intervalA guard interval shall be provided by electronic gating or other equivalent means to prevent the counter fromregistering amplitude hits shorter than 4 ms. The guard interval shall be tested as follows:With a threshold of 2 dB, amplitude hits s
18、hall be counted correctly if the test signal is changed in amplitudeby 3 dB for a duration of 5 ms or more. When the duration of the 3-dB amplitude changes is gradually reduced until theamplitude hit counter stops counting, the corresponding duration of the amplitude changes of the test signal shall
19、be 4 ms 10%.5.3 Hit rate of changeSlow amplitude changes shall not be counted. This characteristic shall be tested as follows:With a threshold setting of 2 dB, an amplitude hit shall be counted when the level of a test signal is linearlyvaried by 4 dB in a time interval of 200 ms or less. An amplitu
20、de hit shall not be counted when the amplitude of the testsignal is linearly varied by 4 dB in a time interval of 600 ms or more. The same requirements shall be met with 4-dBchanges of opposite polarity.5.4 Phase to amplitude conversionA 180 degree phase hit shall not cause an amplitude hit to be co
21、unted at any threshold.6 Count capacityThe counting apparatus shall be equipped with independent phase and amplitude hit counters each having aregister capacity of at least 9999 counts._1)This specification should not preclude the use of existing instruments which have tolerances of 2 5% on the accu
22、racy of thethreshold setting.Fascicle IV.4 - Rec. O.95 37 Counting rate and dead timeThe maximum counting rate for either phase or amplitude hits shall be approximately 8 counts per second,which can be accomplished with a dead time of 125 25 ms after each recognized phase or amplitude hit. For thepu
23、rpose of this specification, the dead time is defined as the time interval that starts when a phase or amplitude hitexceeds the threshold, and ends when the phase or amplitude counter is ready to register another phase or amplitude hit.This characteristic shall be tested as follows:With a threshold
24、setting of 20, phase hits having a duration of approximately 5 ms shall be counted correctlywhen the repetition rate is 5 hits per second or less. When the repetition rate is gradually increased until the phase hitcounter fails to register all counts, the repetition rate shall be 8 hits per second 2
25、0%. The same requirement shall applyto the amplitude hit counter with a threshold of 2 dB when 3-dB amplitude hits having a duration of approximately 5 msare applied.8 Interruption of the test signalIf transmission of the signal is interrupted and the received test signal drops in level by 10 dB or
26、more, thephase and amplitude hit detectors shall be blocked from counting until 1 0.2 s after the test signal is restored. Thereshall be a maximum of 1 phase hit and 1 amplitude hit recorded with each interruption of the test signal.9 TimerA timer accurate to 5% shall be provided for the convenience
27、 of the operator. Periods of 5, 15 and60 minutes and continuous operation should be provided under switch control if the timer is not continuously adjustable.10 Auxiliary logic outputAuxiliary two-state logic outputs shall be provided from the phase and amplitude detectors for recording orcomputer p
28、rocessing of phase and amplitude hit activity. A logic “1” signal shall be output when the hit is present and alogic “0” signal at other times. The output levels shall be compatible with TTL (Transistor-Transistor Logic) integratedcircuits. The output impedance shall be less than 2000 ohms or as spe
29、cified by individual Administrations.11 Operating environmentThe electrical performance requirements shall be met when operating at the climatic conditions as specified inRecommendation O.3, 2.1.12 Simultaneous measurementsThe measurement of amplitude and phase hits may be provided in one instrument
30、 which also makesmeasurements of other transient impairments e.g. impulse noise, interruptions. Therefore, in order to facilitate theintegration of several measurements of transient phenomena into one instrument, the measurement of interruptions inaccordance with the principles of Recommendation O.61, but made with a test signal frequency of 1020 Hz 10 Hzcould be included in such a combined instrument.
