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1991-12-30
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9.Proposed additions and revisions to Recommendation M.1050
LINING-UP AN INTERNATIONAL POINT-TO-POINT LEASED CIRCUIT
The first sentence of 1 of Recommendation M.1050 should be
continued:
"... in Recommendations M.1020 and M.1025) which are provided by
analogue transmission systems or by a mixture of analogue
and digital systems."
The following text should be inserted under the heading "2.1 National
sections":
"When analogue access to the circuit is available at the terminal
international centre the following tests should be performed regardless of whether the
national section is provided by analogue circuit sections or a combination of
analogue, mixed and digital circuit sections."
The following text should be inserted under the heading
"2.2 International section":
"When analogue access to the circuit is available at terminal
international centres the following tests should be performed regardless of whether the
international section is provided by analogue circuit sections or a combination of
analogue, mixed and digital circuit sections."
Add the following text after the first sentence of 3 lining up the
overall circuit:
"It should be noted that satisfactory impulsive noise performance on a
circuit is unlikely to be achieved if the circuit is routed via a primary digital
path on which the bit error ratio exceeds 1.10-6*. It is not intended that this
digital parameter be measured."
Add the following footnote to 3:
"* This parameter is used provisionally and further study is required to assess
whether other parameters (e.g. those in Recommendation G.821) would be more
suitable for relating the performance of transient analogue impairments to the
performance of the digital paths on which the circuits are routed."
The present 3.8 of Recommendation M.1050 should be replaced by the
following:
"3.8 Total distortion (special quality circuits only)
When the circuit includes any digital circuit sections a measurement of
total distortion should be made using an instrument complying with Recommendation
O.132. Such a measurement will include contributions from quantizing distortion, random
noise, harmonic distortion and single tone interference. The minimum signal/total
distortion ratio is given in Recommendations M.1020 and M.1025. However, if this
minimum ratio is satisfied it should not be assumed that all the parameters which
contribute to the measurement are satisfactory. The total distortion measurement is not
a substitute for the individual measurements specified in this Recommendation."
Under the heading "4.1 National sections" insert the same text as given
above for 2.1. Similarly under the heading "4.2 International section" insert the
same text as given above for 2.2.
The same text and footnote given for 3 of this Recommendation should be
added to the end of the first paragraph under "4.1.4. Other characteristics
(special quality circuits)".
The same text and footnote given for 3 of this Recommendation should be
added to the end of the second paragraph under "4.2.4 Other characteristics
(special quality circuits)".
As a consequence of the above-mentioned changes the following text has to
be inserted under the headings of 2.2 and 4.2:
"When analogue access to the circuit is available at the terminal
international centres the following tests should be performed
regardless of whether the international section is provided by
analogue circuit sections or a combination of analogue, mixed
and digital circuit sections."
The title of 3.11 should be changed to:
"3.11 Harmonic and intermodulation distortion (special quality circuits only)"
A new second alinea should be introduced to 3.11 of the Recommendation
as follows:
"Alternatively, by bilateral agreement between administrations, a
measurement of second and third order intermodulation products using an instrument
complying with Recommendation O.42 should be performed. The limit is for further
study."
The following amendments should be made to the second line of 10 of
Recommendation M.1050:
"If there is a breakdown or planned interruption of a transmission
system, rerouting should be carried out as far as possible at group, supergroup or
digital link level. This ... distortion. When such a rerouting of transmission links
cannot be effected ... should be chosen, in particular with regard to the number
of FDM carrier sections and the relative number of analogue and digital circuit
sections. The procedure ...".