3.Proposed amendments to Recommendation 0.41

        PSOPHOMETERS FOR USE AS TELEPHONE-TYPE CIRCUITS
                                Amend second part of section 3.5.1 as follows:



























       For the measurement of AC hum interference on  telephone-type  circuits
an optional low pass filter with a cut-off frequency at approximately  250  Hz
and an attenuation of > 50 dB at 300 Hz may be provided."

       Replace section 3.7 by the following text:

"3.7        Detector and display dynamics (measurement averaging time)

       The response time for the detector and indicating means shall meet  one
or both of the following requirements:

3.7.1   Instrumentation with continuous signal monitoring

       The application of an 800 Hz sinusoidal signal with a duration  of  150
to 250 ms should produce an output indication which is the same as that produced 
by the application of a continuous 800 Hz signal of the same amplitude. Applied 
signals of shorter duration  should  produce  lower  readings  on  the  output
indicator. 

       When performing  this  test  the  reading  error  shall  be  less  than
+ 0.2 dB.
3.7.2  Instrumentation with non-continuous signal monitoring

       With the application of bursts of 800 Hz  tone  to  the  input  of  the
psophometer, gated at a duty cycle of 50%, with half the cycle at full amplitude and 
the other half down 8.4 dB  from  full  amplitude,  the  output  device  shall
indicate a variation as shown below. The levels should be chosen to avoid autoranging 
points.












                 ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
                    Grating    ³  Peak-to-Peak           ³
                    Frequency  ³  Indicator Variation    ³
                 ÃÄÄÄÄÄÄÄÄÄÄÄÄÄÅÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ´
                 ³   25 Hz     ³       < 1 dB            ³
                 ³    5 Hz     ³       > 3 dB            ³
                 ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ

       It is permissible to adjust the total input power with a 1  dB  vernier
control to a point where the display does not change so as to pass the less than 
1 dB requirement."

       Add the following text to the existing Annex A of the Recommendation:

       "Another weighting frequently  used  for  measuring  telephone  circuit
noise impairment within the North American domestic telephone networks is referred 
to as "3  kHz  flat"  weighting  [1].  This  weighting  is  intended  for  the
investigation of the presence of low-frequency noise (power induction, etc.) on the 
circuit under test. It is characterized as a 3 kHz low-pass weighting of Butterworth 
shape attenuating above 3 kHz at 12 dB per octave. The specification for  this
weighting is given in Table A-2/0.41".

                                TABLE A-2/O.41
                                       
                     3 kHz flat weighting characteristic