4.Proposed amendments to Recommendation 0.62

        SOPHISTICATED EQUIPMENT TO MEASURE INTERRUPTION
                  ON TELEPHONE-TYPE CIRCUITS 
       
       Amend section 2.3.1 to read as follows:

"2.3.1      The detector shall respond to a test signal of 2 000 Hz + 100  Hz  (see
also  5)."

          
*  The loss shall continue to increase above 6 000 Hz at a rate of  not  less  than
12 dB per  octave  until  it  reaches  a  value  of  60  dB.  The  loss  at  higher
frequencies shall be at least 60 dB.
       Delete  2.3.3 and 2.3.3.1.

       Insert new  2.4, 2.4.1 and 2.4.2 as given below:

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

       -    Balanced, earth free

       -    Input longitudinal interference loss                  > 46 dB

2.4.1  Terminating impedance (other impedances optional)            600 ohms

       -    Return loss                                           > 30 dB

2.4.2  High impedance                                      approx. 20 kohms

       -    Binding loss across 300 ohms                          < 0.15 dB".  
       Renumber the existing  2.4.2.1 and 2.4.2.2 to " 2.4.3 and 2.4.4".

       Replace section 3 with the following text:

"3.    Display of measurement results

3.1    Interruption counters

       The  detected  interruptions  shall  be  divided  into  the  following  time
categories for recording purposes:

       1)   0.3 (0.6) ms - 3 ms (optional, see note),

       2)   3 ms - 30 ms,

       3)   30 ms - 300 ms, 

       4)   300 ms - 1 min, 

       5)   1 min and over (optional).

       Facility for adjusting to other time groupings may be provided at the option 
of the administrations. The count shall be presented on a visual display.

Note - The value of 0.6 ms applies to the 1 020 Hz test tone.

3.2     Relative duration of interruption events (optional)












       To allow an easier estimation of data transmission errors which  may  result
from interruptions, the instrument shall provide means to calculate and indicate the 
relative duration of interruption events. This quantity is the ratio  of  the  time
where the test tone is below a designated threshold to the total measurement  time.
Interruptions between 3 ms and 1 minute shall be taken into account. Results shall be 
indicated in a range 1 x 10-1 to 1 x 10-8.

3.3    Seconds containing an interruption (optional)

       As a further option, the instrument shall provide  means  to  calculate  and
indicate the percentage of seconds containing one or more interruptions of a duration > 
3 ms. Results shall be indicated in a range 0 to 100%  with  one  digit  after  the
decimal point.

3.4    Power failure

       In the event of a power failure any loss of measurement  results  should  be
clearly indicated on a display for later observation."

       Add a new section 5 to read as follows:

"5.    Simultaneous measurements

       The measurement of interruptions may be provided in an instrument which also 
makes measurements of other transient impairments, e.g., amplitude and phase hits. A 
test signal frequency of 1 020 Hz +2 -7 Hz may be used to facilitate the integration 
of several measurements of transient phenomena in such a combined instrument. In all 
other respects, the measurement of interruptions shall be in  accordance  with  the
principles of this Recommendation."

       The X-axis of Figure 1/0.62 shall be labelled as shown below:















                               Interruption length
                                         
                                  FIGURE 1/O.62
                                         
                       Probability curve for the detection
                                of an interruption