\fI(former Recommendation\ J.14; amended at Geneva,\fR
\fI1972 and 1980, and at Melbourne, 1988)\fR
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.PP
For the alignment of international sound\(hyprogramme connections the CCIR,
in Recommendation\ 661, recommends a \fIthree\(hylevel test signal\fR .
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.RT
.PP
This test signal is based on the test signal definitions given in CCIR
Recommendation\ 645 and specifies a test signal which should be used on
sound\(hyprogramme circuits
generally. A common alignment procedure for
peak programme
meters and
VU\(hymeters
using the three\(hylevel test signal can be found in Annex\ I of CCIR
Recommendation\ 645. From this information it can be seen what indicators
will be produced by the
three\(hylevel test signal
on the different types of
peak programme meters and volume meters.
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.PP
To comply with the provisions of Recommendation\ J.14, the lining\(hyup
and monitoring of an international sound\(hyprogramme connection should ensure
that, during the programme transmission, the
peak voltage at a zero
relative level point
will not exceed\ 3.1\ volts, which is that of a
sinusoidal signal having an r.m.s. value of 2.2\ volts. The methods for
achieving this condition as well as the relevant performance requirements
are given in Recommendations\ N.10 to\ N.18 (see references\ [1] to\ [8]).
.PP
Some indication of the volume or of the peaks of the signals
during programme transmission may be obtained by monitoring at the studio,
in the repeater stations, or at the transmitter. One of the instruments,
the
characteristics of which are summarized in Table\ 1/J.15, may be used.
.PP
Since there is no simple relation between the readings given by
two different instruments for all types of programme transmitted, it is
desirable that the broadcast organization controlling the studio and the
telephone Administration(s) controlling the sound\(hyprogramme circuit
should use the same type of instrument so that their observations are made
on a similar
basis.
.PP
In general the telephone Administration and the broadcast organization
of a country agree to use the same type of instrument. It is desirable
to
reduce to a minimum the number of different types of instrument and to
discourage the introduction of new types which only differ in detail from
those already in service. The unified use of the peak indicator specified
in
reference\ [9] is under study.
.PP
During programme transmission, the signal level at the output of the last
amplifier controlled by the sending broadcast organization (Point\ A of
Figure\ 3/J.13) should be monitored to see that the meter deflection of the
measuring instrument is always lower than the peak voltage for the overall
line\(hyup, allowance being made for the peak factor of the programme
involved.
.PP
It should be remembered that the amplitude range from a symphony
orchestra is of the order of 60 to 70\ dB, while the specification for
sound\(hyprogramme circuits is based on a range of about 40\ dB. Before being
passed to the sound\(hyprogramme circuit, therefore, the dynamic ratio of the
studio output needs to be compressed.
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Blanc
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\fBH.T. [T1.15]\fR
.ce
TABLE\ 1/J.15
.ce
\fBPrincipal characteristics of the various instruments\fR
.ce
\fBused for monitoring the volume or peaks\fR
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\fBduring telephone conversations or sound\(hyprogramme\fR
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\fBtransmissions\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(72p) | cw(36p) | cw(36p) | cw(36p) | cw(48p) .
Type of instrument {
Rectifier
characteristic
(Note 1)
} {
Time to reach 99% of final reading (milliseconds)
} {
Integration time (milliseconds)
(Note 2)
} {
Time to return
to zero
(value and definition)
}
_
.T&
lw(72p) | cw(36p) | cw(36p) | cw(36p) | lw(48p) .
{
(1)
Vu meter (United States of America)
} 1.0 to 1.4 300 165 (approx.) Equal to the integration time
_
.T&
lw(72p) | cw(36p) | cw(36p) | cw(36p) | lw(48p) .
(2) Vu meter (France) 1.0 to 1.4 300 \(+- | 0% 207 \(+- | 0 {
300 ms \(+- | 0% from the reference deviation
}
_
.T&
lw(72p) | cw(36p) | cw(36p) | cw(36p) | lw(48p) .
{
(3)
Peak programme meter, used by the
Netherlands
} 1 Not specified {
10 | s | or | (em1 | B
5 | s | or | (em2 | B
0\(hy4 | s | or | (em15 | B
} {
0 to \(em20 dB: 1\(hy5 |
0 to \(em40 dB: 2\(hy5 |
}
_
.T&
lw(72p) | cw(36p) | cw(36p) | cw(36p) | lw(48p) .
{
(4)
Programme level meter
(Italy)
} 1 Approx. 20 ms Approx. 1.5 ms {
Approx. 1.5 | from 100% to l0% of the reading in the steady
state
}
_
.T&
lw(72p) | cw(36p) | cw(36p) | cw(36p) | lw(48p) .
{
(5)
Peak indicator for sound\(hyprogramme transmissions used by the
British Broadcasting Corporation (BBC peak programme meter)
} 1 10 (Note 3) {
3 | for the pointer to fall 26\ dB
}
_
.T&
lw(72p) | cw(36p) | cw(36p) | cw(36p) | lw(48p) .
{
(6)
Maximum amplitude indicator used by the Federal Republic of
Germany (type\ U\ 21)
} 1 Around 80 5 (approx.) {
1 or 2 | from 100% to 10% of the reading in the steady
state
}
_
.T&
lw(72p) | cw(36p) | lw(36p) | cw(36p) | lw(48p) .
{
(7)
OIRT\ \(em
Programme level meter:
Type A sound meter
Type B sound meter
} {
For both types:
less than 300 ms for meters with pointer indication, and
less than 150 ms for meters with light indication
} 10 \(+- | 60 \(+- | 0 {
For both types:
1.5 to 2 | from the 0\ dB point which is at 30% of the length of the
operational section of the scale
}
_
.T&
lw(72p) | cw(36p) | cw(36p) | cw(36p) | lw(48p) .
{
(8)
E.B.U. standard peak programme meter
(Note 4)
} 1 \(em 10 2.8 | for the pointer to fall 24\ dB
.TE
.LP
\fINote\ 1\fR
\ \(em\ The number given in the column is the index \fIn\fR
| in the
formula \fIV\fR
|
\d(output)
\u\ =\ [\fIV\fR
|
\d(input)
\u]\fI\fI
| applicable for each half\(hycycle.
.LP
\fINote\ 2\fR
\ \(em\ The \*Qintegration time\*U was defined by the CCIF as the
\*Qminimum period during which a sinusoidal voltage should be applied to the
instrument for the pointer to reach to within 0.2\ neper or nearly 2\ dB of the deflection which would be obtained if the voltage were applied indefinitely\*U. A logarithmic ratio of 2\ dB corresponds to 79.5% and a ratio of 0.2\ neper
to\ 82%.
.LP
\fINote\ 3\fR
\ \(em\ The figure of 4 ms, that appeared in previous editions, was
actually the time taken to reach 80% of the final reading with a d.c. step
applied to the rectifying integrating circuit. In a new and somewhat
different design of this programme meter using transistors, the
performance on programme remains substantially the same as that of
earlier versions and so does the response to an arbitray, quasi\(hyd.c. test
signal, but the integration time, as defined in Note\ 2, is about
20% greater at the higher meter readings.
.LP
\fINote\ 4\fR
\ \(em\ This meter is intented specifically for use in monitoring sound
signals transmitted internationally, and therefore incorporates a scale
conforming to CCITT Recommendation\ N.15\ [5], calibrated in dB from
\(em12 to +12 relative to a level marked \*QTEST\*U corresponding to
0\ dBm at a zero relative level point. In addition to the normal mode of
opeation having the characteristics shown above, the meter may be operated
temporarily in a \*Qslow\*U mode faciliting the comparison of observations made at widely separate points. The peak values indicated in this mode have no
absolute significance, and may only be used for such
comparisons.
.nr PS 9
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\fBTableau 1/J.15 [T1.15], p. 7
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\fBReferences\fR
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[1]
CCITT Recommendation \fILimits for the lining\(hyup of international\fR
\fIsound\(hyprogramme links and connections\fR , Vol.\ IV, Rec.\ N.10.
