1、CCITT FASCICLE IV.4 * 48b2.591 0.505886 T 3.7 Sensitivity With the instrument calibrated in accordance with 0 3.6 in the flat condition and the operate level set to O dBm, rectangular pulses of either polarity of 50 milliseconds duration having a peak amplitude of 1.21 V with an interval between pul
2、ses in excess of the dead time shall be applied to the instrument and cause the counter to operate at the correct rate. When the width of these pulses is gradually reduced, the counter shall count at the correct rate when the pulses have a duration of 50 microseconds but shall not count when the pul
3、ses are 20 microseconds. 3.8 Display of measurement results 3.8.1 Impulsive noise counter Each event to be counted shall be recorded as one unit on a counter. The counter shall be able to register at least 999 events. 3.8.2 Relative duration of impulsive noise events (optional) To allow an easier es
4、timation of data transmisison errors which may result from impulsive noise, the instrument shall provide means to calculate and indicate the relative duration of the impulsive noise events. This quantity is the ratio of the time that the input signal exceeds a designated threshold to the total measu
5、rement time. Results shall be indicated in a range of 1 x lo- to 1 x 3.8.3 Seconds containing impulsive noise events (optional) As a further option, the instrument shall provide means to calculate and indicate the percentage of seconds containing one or more occurrences of impulsive noise. Results s
6、hall be indicated in a range O to 100% with one digit after the decimal point. 3.9 Timer A built-in timer capable of switching off the instrument after a predetermined time shall be provided. This timer shall be adjustable from 5 to 60 minutes in steps of 1 minute. Significant testing intervals will
7、 be 5, 15, 30 and 60 minutes. 4 Operating environment The electrical performance requirements shall be met when operating at the climatic conditions as specified in Recommendation 0.3, 0 2.1. Recommendation 0.72 CHARACTERISTICS OF AN IMPULSIVE NOISE MEASURING INSTRUMENT FOR WIDEBAND DATA TRANSMISSIONS (Geneva, 1972) (For the text of this Recommendation see Recommendation H.16 i of Volume III.) Reference CCITT Recommendation Characteristics of an impulsive-noise measuring instrument for wide-band data transmission, Vol. III, Rec. H.16. I 112 Fascicle IV.4 - Rec. 0.72
