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\fBSUPPLEMENTS\ TO\ RECOMMENDATIONS\ IN\fR 
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\fBSECTIONS\ 2\ TO\ 5\ OF\ THE\ SERIES\ G\ RECOMMENDATIONS\fR 
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\fBMONTAGE:\fR PAGE 204 = PAGE BLANCHE
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\fBSupplement\ No.\ 4\fR 
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\fBCERTAIN\ METHODS\ OF\ AVOIDING\ THE\ TRANSMISSION\fR 
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\fIfor this Supplement see page 572, Volume III of the Green Book,\fR \fIGeneva, 
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\fBSupplement\ No.\ 5\fR 
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\fBMEASUREMENT\ OF\ THE\ LOAD\ OF\ TELEPHONE\ CIRCUITS | fR \fBUNDER\ FIELD\ 
CONDITIONS\fR 
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\fIGeneva, 1985)\fR 
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\fBSupplement\ No.\ 6\fR 
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\fBEXAMPLE\ SHOWING\ HOW\ THE\ TOTAL\ VALUE\ OF\ LINE\ NOISE\fR 
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\fBINTO\ ITS\ VARIOUS\ COMPONENTS\fR 
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\fBSupplement\ No.\ 7\fR 
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\fBLOSS\(hyFREQUENCY\ RESPONSE\ OF\ CHANNEL\(hyTRANSLATING\ EQUIPMENT\fR 
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\fBMETHOD\ PROPOSED\ BY\ THE\ BELGIAN\ TELEPHONE\ ADMINISTRATION\fR 
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\fBROLL\ EFFECT\ IN\ COAXIAL\ PAIR\ SYSTEMS\fR 
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\fBSupplement\ No.\ 13\fR 
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\fBNOISE\ AT\ THE\ TERMINALS\ OF\ THE\ BATTERY\ SUPPLY\fR 
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\fBSupplement\ No.\ 17\fR 
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\fBGROUP\(hyDELAY\ DISTORTION\ PERFORMANCE\ OF\ TERMINAL\ EQUIPMENT\fR 
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\fBMATHEMATICAL\ MODELS\ OF\ MULTIPLEX\ SIGNALS\fR 
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\fBEXPLANATORY\ NOTES\ FOR\ THE\ INFORMATION\ OF\ DESIGNERS\fR 
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\fBOF\ A\ MARITIME\ MOBILE\ SATELLITE\ SYSTEM\fR 
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\fI(Geneva, 1980; referred to in Recommendation\ G.473)\fR 
.FS
\fINote\fR \fIof the Secretariat\fR \ \(em\ A revision of Recommendations\ 
G.111\ [1] 
and\ G.121\ [2] has been adopted introducing the new concept of corrected
reference equivalents. The values of reference equivalents are maintained
here for the next Study Period to give planners sufficient time to become
acquainted with the new concepts.
.FE
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\fB1\fR 	\fBAllocation of losses in the maritime system\fR 
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1.1
	\fIComplying with Recommendations\fR 
.sp 1P
.RT
.PP
1.1.1
Figure 1 illustrates the nomenclature adopted in this
Supplement and the arrangements for a 2\(hywire switched shipboard
installation.
.bp
.sp 9p
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure\ 1 p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
1.1.2
The CCITT Recommendations which jointly influence the choice of
the losses in the path (\fIa\fR \ \(em\ \fIb\fR ) and the reference equivalents 
of 
the local system referred to an appropriate set of terrestrial
virtual switching points are as follows:
.LP
	\fIRecommendation G.122\fR \ [3]\ \(em\ To ensure that international
connections have an adequate stability the loss (\fIa\fR \ \(em\ \fIb\fR ) at
any frequency in the band\ 0 to 4\ kHz should not be less
than (6\ +\ \fIn\fR )\ dB where\ \fIn\fR is the number of 4\(hywire
circuits in the national chain.
.LP
	\fIRecommendation G.131\fR \ [4]\ \(em\ When calculating stability the
variations of loss in the two directions of direction
are taken to be fully correlated.
.LP
	\fIRecommendation G.151\fR \ [5]\ \(em\ The standard deviation of
transmission loss for modern national and international
circuits should not exceed 1\ dB.
.LP
.PP
We seek a prima\(hyfacie assurance that the contribution of the
maritime extension to the stability of the 4\(hywire chain is not worse 
than that of a comparable national extension. The factors affecting the 
stability are 
mean departure from nominal, standard deviation of loss, and attenuation
distortion. The mean departure from nominal and standard deviation are 
expected to be about twice the corresponding values for a terrestrial circuit 
so that 
the one satellite circuit can be regarded as having the same effect as four
terrestrial FDM\ circuits when full correlation is assumed. As far as
attenuation distortion is concerned, since the channel equipments in the 
shore station are not in permanent association with those on board ship, 
between\(hychannel variations manifest themselves as another source of variance
among the connections and an allowance of 1\ dB is made for this effect.
.PP
The formula in the Recommendation cited in\ [3] can be rewritten as
(6\ +\ 1\fIn\fR ) in which the coefficient 1\ dB/circuit is explicit rather 
than 
implicit, and we have derived the coefficient\ 4\ +\ 1\ =\ 5\ dB/circuit 
for the case of the satellite circuit. Hence, with\ \fIn\fR \ =\ 1 we obtain 
the condition: 
.RT
.sp 1P
.ce 1000
\fIS\fR \ +\ \fIR\fR \ +\ \fIB\fR \ \(>="\ 11
.ce 0
.sp 1P
.LP
	\fIRecommendation\ G.161, Test\ 8\fR \ [6]\ \(em\ The equivalent level
go/return loss on the office\(hyside of the echo suppressor should not be
less than 6\ dB. In principle, this quantity, which can be derived from
the relative levels at the 2\(hywire switch point, is to be evaluated
under conversational conditions at any frequency within the detection
band of the echo suppressor.
.bp
.LP
	\fIRecommendation\ G.121\fR \ [2]\ \(em\ The various constraints on the
reference equivalents and losses of national systems are as follows,
in which the over\(hybar indicates an average value:
.LP
	\fISRE: | fR 	preferred range: 10 to 13\ dB
.LP
permissible range: 10 to 16\ dB
.LP
	\fIRRE: | fR 	preferred range: 2.5 to
4.5\ dB
.LP
permissible range: 2.5 to 6.5\ dB
.LP
	i.e.:\ 10\ \(=\ 
\fIS\fR \ +\ \fIs | fR \ \(=\ 13 or
16;\ 2.5\ \(=\ 
\fIR\fR \ +\ \fIr | fR \ \(=\ 4.5 or 6.5
.LP
	These values obviously take into account variations although we
shall assume that the variability of \fIs\fR and \fIr\fR are small, i.e.\ that
\fIs | fR \ =\ \fIs\fR and 
\fIr | fR \ =\ \fIr\fR .
.LP
	\fISRE\fR \s6max
.PS 10
\ =\ 21\ dB,\ i.e.:\ \fIS\fR \ +\ \fIs\fR \ \(=\ 21
.RT
.LP
	\fIRRE\fR \s6max
.PS 10
\ =\ 12\ dB,\ i.e.:\ \fIR\fR \ +\ \fIr\fR \ \(=\ 12
.RT
.LP
	These are 97% planning values but we shall take them as 100%
planning values.
.LP
	\fISRE\fR \s6min
.PS 10
\ =\ 6\ dB,\ i.e.:\ \fIS\fR \ +\ \fIs\fR \ \(>="\ 6
.RT
.LP
	Ideally this should take variations into account but the
recommendation is in terms of a planning value.
.LP
	 Difference between the losses (\fIa\fR \ \(em\ \fIt\fR ) and (\fIt\fR 
\ \(em\ \fIb\fR ) 
should not exceed 4\ dB, i.e.:\ | fIS\fR \ \(em\ \fIR\fR |  \(=\ 4.
\v'3p'
.LP
.PP
1.1.3
The Recommendations do not enable us to ascertain the separate
values of \fIS\fR and \fIR\fR because the CCITT does not specify any particular
subdivision of national reference equivalents as between the local system 
and the circuits in the remainder of a national extension. 
.PP
We may simplify the problem by assuming that during the set\(hyup or
clear\(hydown of the connection it is not possible to prevent \fIB\fR \ 
=\ 0, so that 
\fIS\fR \ +\ \fIR\fR \ =\ 11 and furthermore we shall aim to stay within 
the preferred ranges of mean values of the reference equivalents recommended 
for a national 
system.
\v'3p'
.PP
1.1.4
It is clear that within the constraints of:
.sp 1P
.ce 1000
\fIS\fR \ +\ \fIR\fR \ =\ 11;\ | fIS\fR \ \(em\ \fIR\fR |  \(=\ 4;\ | fIS\fR 
\ \(em\ 
\fIS | fR |
\(=\ 0.5;\ | fIR\fR \ \(em\ 
\fIR | fR |  \(=\ 0.5;\ 10\ \(=
\fISRE | fR \ \(=\ 13;\ 2.5\ \(=\ 
\fIRRE | fR \ \(=\ 4.5
.ce 0
.sp 1P
.LP
the individual values of \fIS\fR and \fIR\fR can be chosen to permit a range
of reference equivalents for the shipboard local system as illustrated 
by the solution domains shown in Figure\ 2. We must therefore seek other 
criteria on 
which to base a decision.
.LP
.rs
.sp 21P
.ad r
\fBFigure\ 2 p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
1.2
	\fISubjective criteria\fR \v'3p'
.sp 9p
.RT
.PP
1.2.1
Figure 3, which is based on the corresponding one in
Recommendation\ G.473, illustrates various minimum, average, and maximum
configurations utilizing the information concerning traffic routing
contained in\ [7]. These routings have been used to develop hypothetical
reference connections based on Recommendation\ G.103\ [8] to enable the 
effects of loss, noise, and distortion to be studied in accordance with 
the principles outlined in the CCITT\ manual cited in\ [9]. 
.LP
.rs
.sp 33P
.ad r
\fBFigure\ 3 p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
1.2.2
A few\ \fIS, R\fR and hence \fIs, r\fR \ values within the permitted
solution domains have been studied in order to determine an
optimum set from the point of view of subscriber opinion. The
results of two such calculations are recorded in Table\ 1.
.sp 9p
.RT
.PP
In one calculation the \fIS\fR and \fIR\fR \ values were equal (i.e.: the
\fIS/R\fR differential was zero) and the 
\fISRE | fR and
\fIRRE | fR values were in the middle of their preferred ranges
(
\fISRE | fR \ =\ 11.5; 
\fIRRE | fR \ =\ 3.5;
\fIS\fR \ =\ 5.5; \fIR\fR \ =\ \fIs\fR \ =\ 6; \fIr\fR \ =\ \(em2). In 
the other calculation half the 
permitted \fIS/R\fR \ differential was introduced reducing the
\fIRRE | fR at the expense of the
\fISRE | fR but nevertheless keeping their
values within 0.5\ dB of the extrema of their preferred ranges to allow
for the 0.5\ dB mean departure from nominal in the values of\ \fIS\fR and\ 
\fIR\fR . 
(
\fISRE | fR \ =\ 12.5; 
\fIRRE | fR \ =\ 3;
\fIS\fR \ =\ 6.5; \fIR\fR \ =\ 4.5; \fIs\fR \ =\ 6; \fIr\fR \ =\ 1.5).
\v'3p'
.bp
.LP
.rs
.sp 31P
.ad r
\fBTable 1 T1.23, p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
1.2.3
Table\ 1 shows that moving from the centre of the preferred
ranges has hardly any effect on the opinion scores of the shipboard customer
but has a somewhat greater, worsening effect on the inland customer
particularly on the maximum routing. Hence we advocate arrangement\ B in 
which the\ 
\fISRE | fR and\ 
\fIRRE | fR are at
the middle of their preferred ranges. This arrangement also has the advantage 
that the inland and ship\(hyboard customers' opinions are more nearly equal 
in the case of the average routing (which we must assume will carry the 
most traffic). This is only true for %\fID\fR , not for %\fIP\fR \ +\ \fIB\fR 
. 
.sp 9p
.RT
.LP
.PP
1.2.4
Figure\ 4 illustrates how opinion worsens as the design noise
power
of the maritime satellite system increases from\ 10 | 00\ pW0p (\(em50\ 
dBm0p) to 
100 | 00\ pW0p (\(em40\ dBm0p). These are the effective design noise power 
levels, 
i.e.:\ either an uncompandored noise power level, or the result of a 2:1
compandor with a 0\ dBm0 unaffected level operating on a higher noise power
level, in which case the empirical rule one\(hythird speech\(hyon noise 
power level plus two\(hythirds speech\(hyoff noise\(hypower level was used 
to calculate the 
effective noise (see\ [11]).
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The reference equivalents of the maritime system are
\fISRE | fR \ =\ 11.5 and
\fIRRE | fR \ =\ 3.5. Only the effects of
loss, noise,
bandwidth limitation, and attenuation/distortion have been estimated. The
effects of delay and imperfectly\(hysuppressed echo could not be taken account
of in the calculations but they should not be disregarded.
.bp
.LP
.rs
.sp 22P
.ad r
\fBFigure 4 p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
1.3
	\fIThe preferred arrangement with 2\(hywire switching\fR \v'3p'
.sp 9p
.RT
.PP
1.3.1
Figure 5 illustrates the preferred arrangements upon which
Recommendation\ G.473 is based. All the arrangements are in terms
of the CCITT quantities which relate to virtual switching points
on the international circuit.
.PP
It is clear that \fISRE\fR \s6min
.PS 10
\ \(>="\ 6 is comfortably
met in these arrangements, using planning values. We note that the limit
is also met even when variation is allowed for; the 2.33\ \(*s value for the
mid\(hyrange value of the \fISRE\fR is 11.5\ \(em\ 0.5\ \(em\ 2.33(2)\ 
=\ 6.3 (rounding down to 
the nearest 0.1).
\v'3p'
.RT
.PP
1.3.2
Diagram\ I of Figure\ 6 gives an example of how Arrangement\ I
could be realized in a practical installation. We have assumed
the following:
.LP
	\(em
	actual 4\(hywire switching levels of \(em2\ dBr, which is
typical of many international switching centres;
.LP
	\(em
	a 2\(hywire sending level of 0\ dBr, which is suitable for a
local system with a nominal mid\(hyrange value of sending
reference equivalent of 6\ dB\ (\fISRE\fR ) connected to that
point;
.LP
	\(em
	symmetrical 3.5\ dB terminating units;
.LP
	\(em
	channel translating equipments operated at relative levels
of +4\ dBr/\(em14\ dBr, a pair of levels appearing in
Recommendation\ G.232;
.LP
	\(em
	far\(hyend operated, half\(hyecho suppressors introducing 0\ dB
transmission loss at the appropriate relative levels.
.LP
.PP
1.3.3
It remains to calculate the equal\(hylevel go/return loss on
the office side of the echo suppressor which is seen to be
.sp 1P
.ce 1000
9.5\ +\ 3.5\ +\ B\ +\ 3.5\ +\ 10.5\ \(em\ 18\ =\ 9\ +\ B
.ce 0
.sp 1P
.LP
thus complying with the test conditions of Recommendation\ G.161\ [12]
(assuming no negative B\(hyvalues). The quantity\ 10 can be obtained
with more insight and less arithmetic by taking the difference of
the two relative levels at the 2\(hywire switch point.
.bp
.LP
.rs
.sp 35P
.ad r
\fBFigure 5 p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 43P
.ad r
\fBFigure 6 p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
1.4
	\fIArrangements with 4\(hywire switching\fR \v'3p'
.sp 9p
.RT
.PP
1.4.1
Figure 5 also illustrates two other arrangements which
incorporate 4\(hywire switching: Arrangement\ II which retains a
2\(hywire handset, and Arrangement\ III which is wholly 4\(hywire.
Examples (for guidance only) of the corresponding practicable
realizations are shown in Figure\ 6.
.PP
1.4.2
A half\(hyecho suppressor is shown in Figure\ 6 for the wholly
4\(hywire case. This is to control, if necessary, the echo that
might arise from the acoustical path via the handset of the
shipboard subscriber. The total echo loss demanded between
virtual switching points is effectively 56\ dB (a consequence of
the Recommendations cited in\ [15] and\ [3]). The minimum
(electrical) go/return loss is required to be of the same order
(the Recommendation cited in\ [16]) so as not to nullify the
effect. It is clear that the shipboard installation should aim
at a comparable performance. The recommended values of\ \fIRRE\fR and\ 
\fISRE\fR shown in Figure\ 5 add up to 15\ dB which implies that 
the acoustic go/return loss must fall below 41\ dB. As the
.LP
system designer has no control over how the ordinary subscriber
uses his handset there is a prima facie case for assuming little
possibility of being able to guarantee this value. However,
there is little experimental data on this topic and further
study is desirable. The results of such a study may indicate
that suppressors can be dispensed with in wholly 4\(hywire
installations. Four\(hywire head and breast sets (or press\(hyto\(hyspeak
handsets) used for special purposes by trained persons would be
less troublesome in this regard and it is unlikely that a
ship\(hyboard suppressor would be needed for these cases.
.sp 1P
.LP
1.5
	\fITaking advantage of a non\(hyzero stability balance return loss\fR \v'3p'
.sp 9p
.RT
.PP
1.5.1
All the allocations of loss shown for a 2\(hywire
local system tacitly assume that during set\(hyup or clear\(hydown
there is the possibility of zero balance return loss at the
2\(hywire/4\(hywire terminating set. However, if special
arrangements are made, as indicated for example in
Recommendation\ Q.32\ [14] so that at all
times a certain minimum positive value is assured, there can be
corresponding reductions of the\ \fIS\fR , \fIR\fR \ values and increases
of the\ \fIs\fR , \fIr\fR \ values.
.LP
.PP
1.5.2
The arrangements of Recommendation Q.32\ [14] introduce a
minimum of 6\ dB balance return loss and assuming this to be less than the
off\(hyhook balance return loss of the shipboard local system,
the\ \fIS\fR and \fIR\fR \ values could be reduced by 3\ dB each and
the\ \fIs\fR , \fIr\fR \ values correspondingly increased. Other partitions
are possible, provided they comply with constraints given in
\(sc\ 1.2 above. It is clear that if\ \fIS\fR and\ \fIR\fR can be
reduced in this way there is more scope for catering for a range
of existing shipboard local systems.
.sp 2P
.LP
\fB2\fR 	\fBEstimated speech power levels and signal\(hyto\(hynoise ratios\fR 
.sp 1P
.RT
.sp 1P
.LP
2.1
	\fISpeech power levels entering the maritime system at the shore\fR 
\fIstation\fR \v'3p'
.sp 9p
.RT
.PP
2.1.1
We can estimate the mean and standard deviation of the speech
power levels at the shore station by considering the relevant
Recommendations. Naturally this is not claimed to be the
same as measured values, but it is probably the best we can do
for planning purposes, particularly since traffic\(hyweighted
values are not really appropriate for equipment design if a
worldwide service is planned for.
.LP
.sp 1P
.LP
2.1.2
	\fIRecommendation G.121\fR \ [2]: National systems
.sp 9p
.RT
.PP
Mean\ \fISRE\fR calculated to international virtual analogue
switching points:\fR 13\ dB
.PP
Range is (21\ \(em\ 6)\ =\ 15\ dB from which, as an approximation,
standard deviation\ =\ \(14 (range)\ =\ 3.8\ dB.
.RT
.sp 1P
.LP
2.1.3
	\fIRecommendation P.16\fR \ [17]: Crosstalk
.sp 9p
.RT
.PP
Conversational speech power level from an active median
talker via a 0\ dB \fISRE\fR \ end is \(em6\ dBm; standard deviation is
4.8\ dB.
.RT
.sp 1P
.LP
2.1.4
	\fIAnnex 2, Question\ 1/XVI\fR \ [7]: International 4\(hywire chain
.sp 9p
.RT
.PP
From the statistics of the international 4\(hywire chain recorded in\ [7] 
we obtain the estimate of the mean and the variance of the transmission 
loss of this portion of the connection shown in Table\ 2, assuming that 
the circuits 
comply with the provisions of Recommendation\ G.151\ [18] in respect of 
standard deviation. 
.bp
.RT
.LP
.rs
.sp 13P
.ad r
\fBTable 2 T2.23, p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
2.1.5
Combining all these estimates, the distribution of speech power
levels at the input to the maritime system at the shore station
we obtain:
.sp 1P
.ce 1000
Mean = \(em13\(em6\(em0.6 = \(em19.6 dBm
\v'6p'
.ce 0
.sp 1P
.ce 1000
Standard deviation = 
@ sqrt { .8~\u2\d~+~4.8~\u2\d~+~1.108 } @  = 6.2 dB
.ce 0
.sp 1P
.LP
.sp 1
.PP
2.1.6
We can reasonably assume \(em3.5\ dBr to be the relative level at
the input to the maritime system directly connected to the
receive virtual switching point of the international circuit
delivering the signal, although strictly speaking there is no
recommendation concerning the relative level at these points
on the \*Qnational\*U side of the virtual switching points.
.PP
2.1.7
Hence we finally obtain as a defensible system planning value:
.LP
	Mean\ =\ Median\ =\ \(em16.1\ dBm0
\v'2p'
.LP
Standard Deviation\ =\ 6.2\ dB.
.sp 1P
.LP
2.2
	\fISpeech power level at the input to the maritime system from the\fR 
\fIshipboard local system\fR 
.sp 9p
.RT
.PP
In any studies concerning a fixed threshold setting (e.g.\ for echo suppressor 
or noise squelch circuit) it should be noted that the mid\(hyrange 
value of the sending reference equivalent referred to a 0\ dBr\ point for the
shipboard local systems illustrated in Figure\ 6 is 6\ dB corresponding to a
mean active speech power level of \(em11.5\ dBm0, so that\ 99% of talkers 
would not fall below\ \(em12\ \(em\ 2.33(4.8)\ =\ \(em23.5\ dBm0. This 
would thus be a suitable level 
for a threshold detector based on mean active power level. A detector
responding to syllabic power levels would need to be set somewhat lower if
centre clipping effects are to be avoided. If an increase of the \fIs\fR 
\ value 
is foreseen (as a result of the considerations outlined in \(sc\ 1.5.2
above) the mean active speech power level will be correspondingly reduced.
.RT
.LP
.sp 1P
.LP
2.3
	 \fIDistribution of speech signal\(hyto\(hynoise ratios at the output 
of the\fR \fImaritime system on board ship\fR \v'3p' 
.sp 9p
.RT
.PP
2.3.1
What follows is an elementary estimate of the distribution of
the speech signal\(hyto\(hynoise ratio in a switched telephone network, in
which there is a distribution of speech volumes, using a
maritime satellite system achieving the long\(hyterm aim of a
design noise power level of\ \(em50\ dBm0p (10 | 00\ pW0p) regarded
as essentially constant for most of the time. This, of course,
represents a reversal of the basis on which conventional
HF\ radio circuits are designed in which the speech volume is
assumed to be held substantially constant by means of a constant
volume amplifier (or a technical operator), and the noise
being regarded as the variable.
.bp
.LP
.PP
2.3.2
\fISignal\fR \ \(em\ Since the distribution of speech volumes is
substantially log\(hynormal, the speech power level of the active
median talker is given by:
.sp 1P
.ce 1000
10\ log\d1\\d0\u(mean power/1\ mW)\ \(em\ 0.115\ \(*s\u2\d
.ce 0
.sp 1P
.LP
where \(*s\u2\d is the variance of the distribution of speech power levels.
Allowing, say 2\ microwatts for echos and other currents, the conventional 
load for the speech power at a 0\ dBr\ point averaged over all channels 
is 
20\ microwatts and the conventional activity factor is\ 0.25. Hence the
(conventional) mean active speech power is 80\ microwatts. The standard
deviation of speech volumes is of the order of 6.2\ dB (see \(sc\ 2.1.5 
above). We obtain from these figures: 
.LP
	speech power level of the active median talker
.LP
= 10 log\d1\\d0\u(80/1000)\ \(em\ 0.115(38.44)\ =\ \(em15.4\ dBm0
.PP
\fINoise\fR \ \(em\ In the case being considered, i.e.\ the long\(hyterm aim,
the constant equivalent value is \(em50\ dBm0p.
\v'3p'
.LP
.PP
2.3.3
Hence, the mean signal\(hyto\(hynoise ratio
\fIQ | fR , is
\fIQ | fR \ =\ 
\fIS | fR \ \(em\ 
\fIN | fR 
=\ \(em15.4\(em\ (\(em50)\ =\ 34.6\ dB.
\fIQ\fR is normally distributed with a standard deviation of 6.2\ dB, and the
principal source of variation in the signal level will arise either from
different talkers on the various channels provided by the maritime satellite
link, or from successive talkers on a particular channel, i.e.:\ it is 
assumed that the process is essentially ergodic. Hence we can construct 
Table\ 3 showing the various percentages of time (to the nearest\ 1%) for 
which particular values of signal\(hyto\(hynoise ratios are exceeded by 
setting \fIk\fR \ =\ (\fIQ\fR \ \(em\ 34.6)/6.2 and 
consulting tables of the normal variate.
.LP
.rs
.sp 23P
.ad r
\fBTable\ 3 T3.23, p.\fR 
.sp 1P
.RT
.ad b
.RT
.PP
2.3.4
In the case of the short\(hyterm limits for noise, Figure\ 4/G.473
defines the following functional relationships between\ \fIS\fR (speech
signal) and\ \fIQ\fR (signal/noise ratio) as
\v'6p'
.sp 1P
[Formula Deleted]
.ce 1000