5.Proposed revisions to Recommendation 0.71 
IMPULSIVE NOISE MEASURING EQUIPMENT FOR TELEPHONE-TYPE CIRCUITS

       Replace existing  3.1, 3.1.1 and 3.1.2 by:

"3.1   Input impedance (frequency range 300 Hz to 4 kHz)

       -    Balanced, earth free

       -    Input longitudinal interference loss              > 46 dB
             3.1.1 Terminating impedance (other impedances optional)       600 ohms

       -    Return loss                                       > 30 dB

3.1.2  High impedance                                  approx. 20 kohms

       -    Bridging loss across 300 ohms                     < 0.15 dB"

       Add new sentence, table and note at the end of section 3.5.2:

       "For measurements of impulsive noise  with  a  1  020  Hz  test  signal  (see
Recommendation 0.6) applied to the circuit under test, a notch filter at        1 020 Hz 
shall be provided as an option. This filter shall have the following characteristics:









Note - It should be noted that measurement results may differ  if  measurements  are
performed with and without test tone.

       Replace section 3.8 with the following text:

"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 estimation of data transmission 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  measurement
time. Results shall be indicated in a range of 1 x 10-1 to 1 x 10-8.

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 shall be indicated in a range 0 to 100% with one  digit  after  the  decimal
point.