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Патент USA US3049604

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Aug- 14, 1962
w. SONNEBORN
3,049,596
CARRIER FREQUENCY COMMUNICATION SYSTEM
Filed Aug. 1, 1960
Inventor‘
M swam
M W<.,_ M
2
2
meat the above mentioned “loop-gain method” for meas
3,649,596
uring the aging of the repeater stations by utilizing the
non-linearity thereof for forming modulation products
SYSTEM
which in some way cooperate with the test frequency or
a multiple thereof. However, these known methods en
CARRER FREQUENCY CQMMUNHCATEQN
Willi Sonnehorn, Bergiscii-Gladbaeh, Germany, msignor
to Feiten & *Guiiieaume Cariswerk A.G., Kohl-Mui
heim, Germany
Filed Aug. 1, 1969, Ser. No. 46,582
Claims priority, application Germany Aug. 3, 1959
9 (Ziaims. (Cl. 179—175.31)
The present invention refers to a carrier frequency com
munication system with two terminal stations and a plural
ity of usually unattended intermediate two-way repeater
stations, operating according to the two-way two-band
method which means operation with two-separate carrier
frequency bands spaced from each other. The range of
frequencies located between the two carrier frequency
bands used for communication will be called hereinafter
the intermediate frequency range.
More particularly the invention concerns a system for
testing the operativeness of the individual intermediate
repeater stations.
If in carrier frequency communciation systems unat
tail the disadvantage that during the testing of the particu
lar repeater station the same frequency product is also
produced to a greater or lesser degree by the other existing
repeater stations, i.e., all or at least a plurality of the exist
10 ing repeater stations of a system are somehow participat
ing in the expected modulation product so that the indica
tions or observations obtained by such a test are not un
equivocal.
It is therefore a main object of this invention to provide
for a system for the purpose set forth above, encompass
ing the advantages of the above mentioned known meth
ods while avoiding their disadvantages.
It is another object of this invention to provide for a
test system for repeater stations which is entirely reliable
and requires a minimum of components of comparatively
simple structure in each repeater station.
With above objects in view the invention provides in a
carrier frequency communication system with two termi
tended repeater stations are provided, then it is necessary
to check or test their operativeness or electrical behavior
by procedures established or carried out in an attended
nal stations and at least two intermediate two-repeater sta
station, usually one or the other of the terminal stations of
the system. The purpose of such remote checking is to
locate geographically that repeater station which is either
defective or unoperative or which displays changes of cer
transmission means connecting in tandem arrangement
said terminal and repeater stations for transmitting mes
tain electrical characteristics which would indicate aging
whereby either the performance or the quality of the trans
mission is degraded or is likely to cause such degradation
carrier frequency band in the opposite direction; each re
peater station comprising ?rst and second frequency-selec
in the near future. It is therefore desired not only to lo
cate in-operative repeater stations for the purpose of re
pair or exchange, but also to determine from time to time
tively adjoining portions of said transmission means for
which repeater appears to be aging prematurely and there
fore should be exchanged or repaired as a matter of pre
tions operating with two separate carrier frequency bands
spaced from each other, in combination, two-conductor
sages between said terminal stations by means of a higher
carrier frequency band in one direction and of a lower
tive direction control means connected between respec
selectively passing said higher and lower frequency bands,
respectively, in said respective directions between said por
tions, one-way ampli?er means having input and output
terminals, respectively, and being associated with said di
rection control means for amplifying said higher and
caution.
Several methods of carrying out checks of the above 40 lower frequency bands, respectively, and frequency-selec
tive frequency-multiplier means connected between said
mentioned nature are known. ‘One of these methods is
output terminal and a junction point between an adjoining
called “loop-gain method.” According to this method the
portion of said transmission means and that input end of
ampli?cation of signals carried out by the individual re
said selective direction control means where said higher
peater stations is measured by transmitting from one ter
carrier frequency band is received, for applying the output
minal station a test freqency within the lower communi
frequency of said multiplier means to at least one of said
cation carrier frequency band for every repeater station,
?rst and second direction control means, said frequency
this test frequency being transformed by the respective re
peater station through certain auxiliary equipment into
mutliplier means being capable of selectively multiplying
the upper carrier frequency band so that the test signal 50 only a discrete test frequency preassigned to and distinc
tive of the particular repeater station and located within
is returned within the upper carrier frequency band
the intermediate frequency range between said higher and
through the regular communication means to the terminal
lower carrier frequency bands and of delivering an output
station which has transmitted the test frequency. The dis
frequency higher than the lowest one of said higher fre
advantage of this method consists in the fact that repeater
quency band, whereby two selected auxiliary frequencies
stations which are aging prematurely cannot be recognized
transmitted for testing any speci?c one of said repeater
and that in the case of inoperativeness of one particular re
stations from one of said terminal stations toward the
peater station those other repeater stations located on the
other terminal station will form through superposition a
remote side of the defective repeater station cannot be
test frequency which is distinctive of said speci?c one of
reached anymore by the respective test frequency whereby
said repeater stations and located within said intermediate
a testing of those other repeater stations is made impos
frequency range and therefore will be multiplied by the
sible.
frequency-multiplier means of that speci?c repeater sta
In other known methods modulation products are used
tion and returned to said one terminal station through said
for testing the repeater stations. However, this method
requires additional components in the repeater stations
transmission means provided that said speci?c repeater
which are highly undesirable in view of the desire of pro
station is operating properly.
viding for a long service life expectancy for the repeater
stations, also such additional components require addi
tional space, or in the terminal stations auxiliary equip
ment would have to be provided which is generally alien
to the carrier communication system, as for instance im
pulse generators or the like.
Moreover certain methods are known which supple
In a preferred embodiment of the invention, in each re
peater station only one single one-way ampli?er is pro
vided which is so connected between said ?rst and second
frequency-selective direction control means that both the
higher carrier frequency band and the lower carrier fre
quency band are directed through the one ampli?er and the
respective high frequency and low frequency signals are
3,049,596
4
ampli?ed thereby. If now two selected different fre
quencies f1 and f2 are transmitted from one of the two ter
minal stations at suitable volume and within the frequency
peater stations regarding the noise production thereof
caused by intermodulation.
band associated with that particular station, then, in View
of the non-linearity of the above mentioned ampli?er in
istic for the invention are set forth in particular in the ap
pended claims. The invention itself, however, both as to
a repeater station a modulation product fr=nf1imf2 is
its construction and its method of operation together with
additional objects and advantages thereof, will be best
understood from the following description of speci?c em
The novel features which are considered as character
produced by superposition of the above mentioned fre
quencies at the output terminal of the ampli?er and this
modulation product constituting the test frequency is lo
cated in the intermediate frequency range and is deter
mined by the selection of the ?rst mentioned frequency 7'1
and f2 to be the test frequency distinctive of and preas
10
bodiments when read in connection with the accompany
ing drawing in which:
FIG. 1 is a schematic circuit diagram illustrating a car
rier frequency communication system incorporating the
signed to one particular of one of the repeater stations in
invention in the form of one preferred embodiment there
the system. For obvious reasons the factors It and m are
of, only those components of the system being shown
small integer numbers.
In a preferred embodiment of the invention and for
practical purposes the frequency multiplier means are fre—
quency doublers. Consequently, the above mentioned
15 which are necessary for understanding the invention; and
FIG. 2 is a graph illustrating for the frequency-selective
direction control means of every one of the three repeater
stations illustrated by FIG. 1, the attenuation versus fre
quency characteristics thereof. The ‘broken lines separat
ing the individual graphs are intended to indicate the re
and this doubled test frequency is applied to that end of
lation between the individual graph and the respectively
the selective direction control means where the higher fre
associated repeater station shown in FIG. 1.
quency band is received so that this doubled test frequency
Referring now to FIG. 1, the illustrated carrier fre
can now be transmitted through the transmission means
quency communication system comprises two terminal
back to the one terminal station from which the frequen
cies f1 and f2 have been transmitted because this doubled 25 stations A and B and three intermediate two-repeater
staions V1, V2 and V3, connected in tandem arrange
test frequency is located within or slightly above the
ment between the terminal stations by the transmission
above-mentioned higher carrier frequency band. The
means e.g. a cable K having certain portions extending
above statement applies particularly if the just-mentioned
between the terminal stations and the individual repeater
frequencies have been transmitted from that one terminal
station which usually transmits signals Within the lower 30 stations, respectively. Of course, the system may com
prise many more repeater stations.
carrier frequency band. However, additionally a second
Each repeater station comprises, in this embodiment, a
modulation product is obtained at the tested repeater sta
single one-way ampli?er AV and frequency-selective di
tion from mixing the above-mentioned doubled test fre
rection control means. The latter comprise a pair of high
quency with another frequency e.g. the usually available
pass ?lters HP1, HP2 and a pair of low pass ?lters TPl
pilot frequency. This is applicable when the primary fre
and TP2, connected between the adjoining portions of the
quencies f1 and ]‘2 are transmitted from the other terminal
cable K and the ampli?er AV, and with the latter, in
station Within the higher carrier frequency band because
output frequency fr of each particular ampli?er is doubled
in this case the doubled test frequency mixed with e.g. the
the manner shown in FIG. 1 so that messages transmitted
pilot frequency produces a modulation product which is
from the terminal station A within the lower frequency
located within the lower frequency band so that this sec 40 band :as well as messages transmitted from the other
ond modulation product can be received by the just-men
tioned other terminal station which usually operates over
terminal station B toward the other station within the
higher frequency band are directed through the ampli?er
AV. In each repeater station the output terminal of the
ampli?er AV is connected to the input of a frequency
multiplier, or more particularly a frequency doubler T.
transmitted from one of the terminal stations and which
usually is located close to the upper boundary of the 45 The output terminal thereof is connected with that end
of the particular repeater station, or more speci?cally with
higher carrier frequency band.
that end of the respective direction control means which
From the above it can be seen that the system accord
are arranged to receive the higher frequency band trans
ing to the invention makes it possible to check and test
mitted from the station B.
each repeater station of a system individually and to ob
As has been stated above, upon transmission of two
tain information about the operativeness or the electrical
selected .auixliary frequencies within the respective carrier
performance thereof, and in addition to locate those re
frequency band from either one of the terminal stations
peater stations which are not in operative condition. This
AB, a modulation product serving ‘as the characteristic
is done by transmitting selected freqencies from either one
of the two terminal stations for the purpose of forming 55 test frequency fr for a repeater station will be formed at
the output terminal of the respective ampli?er AV and will
modulation products which are located within the interme
be reapplied as ‘a doubled test frequency Zfr to the trans
diate frequency range and by transposing such modula
mission means. It is essential that each of the frequency
tion products into other frequencies, either directly or by
multiplier or frequency doubler devices T of generally
forming a second modulation product with the aid of
other frequencies, with the result that in any casea signal 60 known type is frequency-selective in itself so that in each
particular repeater station the respective‘ device T will
representative of the performance or operativeness (or
multiply or double only one particular test frequency
non-operativeness) of any one individual repeater station
speci?cally preassigned to that particular repeater station
is returned to that terminal station from which the testing
and therefore distinctive thereof. This can be achieved
procedure has been initiated.
in generally known manner by means of resonance cir
It is to be noted that furthermore, when the signal trans 65 cults or similar means within the frequency multiplier or
the lower frequency band. As is Well known, the pilot
frequency is a frequency signal which is continuously
mission through carrier frequency transmission is stopped,
frequency doubler T.
also noise components e.g., tube noise within the range of
the individual respective test frequency can be doubled or
teristics of one high pass ?lter HP {and one low pass ?lter
The graphs of FIG. 2 illustrate the attenuation charac
TP of the corresponding repeater station, the attenuation
multiplied by the frequency multiplier means in the in
dividual repeater stations and will be thereafter ampli?ed 70 curve being marked accordingly. In each graph the
abscissa represents the frequencies f in kilocycles and the
by the respective ampli?er means and returned within the
ordinate indicates the attenuation b in Nepers, The
higher carrier frequency band to the particular terminal
marking fu represents the upper boundary of the lower
station. In this manner the system according to the in
vention can be utilized also for checking the individual re 75 carrier frequency band, and the marking f0 indicates the
lower boundary of the upper carrier frequency band.
3,049,596
5
Consequently, the difference Af=fo—fu would be the
above mentioned intermediate frequency range. As would
be understood from the above, the lower carrier frequency
band having the upper limit frequency fu is transmitted in
the direction from station A to B, while in the direction
from the station B to the station A the upper carrier fre
quency band with a lower limit frequency f0 is trans
mitted.
The existence of this intermediate frequency range can
be used according to the invention to great advantage for 10
the purpose to prevent the modulation product or test
frequency fr appearing at the output of each of the ampli
?ers of the various repeater stations from being applied
through the transmission means to the other repeater
Assuming, for example, that from the terminal station
A two auxiliary frequencies f; and f2 at a suitable prede
termined amplitude are transmitted toward the station B
by means of the lower carrier frequency ‘band, and as
suming further that the just mentioned two auxiliary fre
quencies are so selected that a strong modulation product
or test frequency fr=nf1+mf2 is formed which is located
in the reduced intermediate frequency range ML and is
identical with a preassigned test frequency of a particular
repeater station, then the frequency doubler T of a par
ticular repeater station and selectively capable of doubling
only that particular test frequency will produce an output
frequency 2(nf1imf2). By properly selecting the aux
iliary frequencies f1 and f2 the doubled test frequency
stations and particularly to the respective ‘ampli?ers there 15 will be located within or slightly above the higher car
rier frequency band and can therefore be transmitted
of whereby modulation products intended to be formed
through the high pass ?lter H132, the associated ampli
there would be affected.
?er AV (with ampli?cation thereby), the associated high
For achieving this advantage the ‘arrangement must be
such that the modulation products or test frequencies A
pass ?lter HPI and through the transmission means, pos
are so located within the intermediate frequency range 20 sibly including other repeater stations, back to the termi
that they are su?iciently ‘attenuated both by the low pass
?lters and by the high pass ?lters. ‘Such minimum attenu
ation is indicated in FIG. 2 by the level lines 170 and
should be for practical purposes at least 3 Neper. As
nal station A. By measuring the amplitude of that dou
bled test frequency upon arrival at the terminal station A
the electrical condition or performance of the ampli?er
AV of the particular tested repeater station can be judged.
In a similar manner it is possible according to the in
can be seen also from FIG. 2 the attenuation curves 25
vention to locate any repeater station which has become
HP and TP intersect the horizontal lines he. The curve
inoperative. For instance the inoperativeness ‘of the re
TP has an intersection point corresponding to a frequency
peater station V2 can be determined by the application of
in. Frequencies above fLl are subjected to a greater at
the above described procedure as follows: If in the man
tenuation than 150 as is indicated by the shape of the
curve TP. In the case of the high pass ?lter the re 30 ner described above different combinations of auxiliary
frequencies f1 and f2 are sequentially transmitted by
quired minimum attenuation b0 corresponds to a fre
means of the lower carrier frequency band from the ter
quency fL-z and the attenuation would increase for fre
minal station A, then, if all repeater stations are in good
operation condition, the doubled modulation products or
frequency range AfL indicated between fm and fLz then 35 test frequencies respectively produced in all of the re
peater stations would 'be received in the terminal station
one can be sure that a test frequency f, located within
A through the higher carrier frequency band. However,
the just mentioned smaller intermediate frequency range
e.g. if the repeater station V2 has become inoperative,
will be attenuated both by the low pass ?lter and by the
then only the doubled test frequency characteristic of
high pass ?lter to a degree at least equal to the indicated
minimum attenuation be. However, between the output 40 the repeater station V1 will be returned from that repeat
or station, but no doubled test frequency will be returned
terminal of each ampli?er AV and the input terminal
from the repeater station V2 and also not ‘from any one
of the next following ampli?er AV the test frequency fr
of the repeater stations beyond the station V2 as seen
located within the frequency range AfL will be subjected
from the station A. Thus in the station A it is deter
to a total attenuation b52170 because the frequency f,
has to pass through two low pass ?lters or two high pass 45 mined that the repeater station V2 is inoperative, but it
is still possible that also one of the other repeater sta
?lters, as the case may be. Any additional attenuation
tions beyond the station V2 is defective. In order to
caused by the interposed cable portions can be disregarded
determine whether this is so, two other auxiliary fre
because this attenuation is compensated ‘by the ampli?ers.
quencies f1 and f2 located within the higher carrier fre
By suitably choosing the magnitude of the required mini
mum attenuation b0 resulting in corresponding narrowing 50 quency band are transmitted from the terminal station B.
It is possible to obtain from these auxiliary frequencies
or widening of the intermediate frequency range AfL it
a doubled test frequency located in the higher carrier fre
can be arranged that the modulation product or test fre
quency band, but such ‘doubled test frequency could vbe
quency 7‘, is suf?ciently attenuated to be prevented from
received in the terminal station A only if the repeater sta
reaching ‘any one of the subsequent repeater ampli?ers.
Consequently, at the output terminal of the individual 55 tion V2 were not inoperative and if all other repeater sta
tions were in good condition. In any case, the path from
ampli?ers AV only that one modulation product or test
the station E to the station A is now blocked by the de
frequency fr will ‘be present which is formed in that par
ticular repeater station.
fective repeater station V2. In order to be able to re
ceive in the terminal station B an indication about the
The individual different test frequencies f, preassigned
to and distinctive of the respective repeater stations are 60 condition of the repeater station between the terminal sta
quencies lower than fLz.
Therefore, if the modulation
product or test frequency 1’, is located within the reduced
selected in such a manner that they are located within
tion B and the defective repeater station V2, a third aux
iliary frequency located in the upper carrier ‘frequency
band is required. Such third auxiliary frequency could
be transmitted from the terminal station E, but for the
and f2 may be transmitted either from the station A or
from the station E, or one of them may be transmitted 65 sake of convenience the usually available pilot frequency
is preferably used for this purpose. The pilot frequency
from the station A and the other one from the station
the intermediate frequency range AfL. Basically, the
above mentioned two selected auxiliary frequencies ]‘1
E in each case the auxiliary frequency must ‘be located
Within the carrier frequency band assigned to the par
ticular terminal station. Ordinarily it is desirable that
the doubled or multiplied modulation product or test fre
quency fl, is located close to the upper boundary of the
higher carrier frequency band so that it can be transmit
ted from the respective repeater station back to the termi
nal station A. However, a modi?cation of this system
will be described further below.
75
has 1been de?ned further above in the speci?cation. The
third auxiliary frequency is to be chosen, and the pilot
frequency is in any case suitable, to form with the dou
lbled modulation product or test frequency located, as
stated above, within ‘the upper carrier frequency band,
a further modulation product which however will be lo
cated within the lower carrier frequency band and there
fore this further modulation product being indicative and
characteristic of a particular repeater station located be
3,049,596
8
B. Testing of Repeater Stations, Finding
tween the station B and the repeater station V2 will 'be
transmitted back and can be received by the terminal
That V2 Is Inoperative
The following auxiliary frequencies f1 and f2 are trans
station B. Thus the arrival or non-arrival of the last
mentioned modulation product at the station B will in
dicate Whether a repeater station between terminal sta
mitted from the terminal station A for testing ?rst the re
peater station V1 and then the station V2, with the result
tion B and the repeater station V2 is operative or defec
that the corresponding doubled modulation products or
tive, respectively.
test frequencies 2]‘T are received back or not received:
From the above it can be seen that it is possible accord
ing to the invention to transmit properly selected auxiliary
f1,
frequencies f1 and f2 from the terminal station A as Well
as from the terminal station B, or one of these frequencies
from the station A and the other one from the station B,
in each case of course within the carrier frequency band
Re eater:
assigned for the transmission from the particular terminal
the terminal station A by transmission within the higher
carrier frequency band. However, if a modulation prod
uct is to be received also in the terminal station B then a
third auxiliary frequency transmitted either from the sta- '
tion A or from the station B is mixed with the above men
tioned doubled modulation product or test frequency lo
cated in the higher carrier frequency band so as to form a
further modulation product which is then located within
volume ‘of the modulation products received at the termi
nal stations at a volume which is close to the volume range
limit of the ampli?ers AV because in this area the volume
of the modulation products increases steeply and aging of
the ampli?er components would produce relatively great
changes.
kc.
(fl‘i‘f?)=fn
kc.
2(f1+f2)=2fn
kc.
Remarks
pV1_____
135
153
288
576
Received.
V2"..-
135
153.1
288.1
576.2
Net
_
received.
station. The only condition is that as a rule the doubled
modulation product or test frequency can be received in
the lower carrier frequency range and can therefore be
‘returned to and received by the terminal station B.
In order to increase the sensitivity of the above proce
dure it is advisable to measure by well known means the
f2,
kc.
Now, since V2 has been found inoperative, the follow
ing auxiliary frequencies f1 and f2 are transmitted from the
terminal station B for testing the repeater stations V2 and
V3, with the results marked below:
Repeater:
_
Va___.
500
394.1
288.2
576.4
23.4
Received.
V2.--_
500
394.05
288.1
576.2
23.2
Not
_
received.
It will be understood that in the just charted example
the characteristic of the ampli?ers is such that in the pre
viously used equation the factor n is 2 and the factor m
is 1. Moreover, the doubled test frequency 2f, is mixed
with the pilot frequency fp for obtaining a further modu
lation product as indicated in the last ?gure column of
the above chart.
As can be seen the result of the last de
NUMERICAL EXAMPLE
scribed test is that the repeater station V3 is in operative
May it be assumed that the communication system com
is con?rmed.
If it is desired to check also in accordance with the in
vention on the noise conditions of the individual ampli
?ers or repeater stations, then, for obtaining as high a
noise level as possible, the frequency-selective elements of
the arrangement are suitably constructed or chosen in such
condition while the non-operativeness of the station V2
prises the repeater stations V1, V2 and V3. The system
may be operating with 60 channels and the lower carrier
frequency band may comprise frequencies between 24 and
264 kilocycles, and the higher carrier frequency band may
comprise frequencies between 312 and 552 kilocycles.
The pilot frequency fp may be 553 kilocycles. The attenu
ation b0 may have been chosen to amount to 4 Neper de
a manner that these frequency-selective elements transmit
a frequency band of a certain width
termining for the low pass ?lters a frequency fm of 283
kilocycles and for the high pass ?lters a frequency in of
290 kilocycles. Consequently the reduced intermediate
wherein A is the number of repeater stations in the whole
frequency range AfL amounts to \290-283=7 kilocycles.
transmission system. This means that the available band
If the spacing between the individual test frequencies is
chosen to be 0.1 kilocycle then it would be possible to test 50 Width of the intermediate frequency range Jig-in is com
pletely and evenly distributed among the repeater stations
71 intermediate repeater stations Within the range of 7
of the Whole transmission system. The frequencies within
kilocycles. However, in the present example only the
this band width are then doubled by the frequency doubler
test frequencies for 3 intermediate repeater stations are to
be determined. Therefore these 3 test frequencies are as
signed to the 3 repeater stations as follows:
means and are returned, exactly as the above mentioned
doubled test frequencies, via the high pass ?lters HP2, the
respective ampli?ers AV (With ampli?cation thereby) and
via the respective high pass ?lters HP1 by means of the
higher carrier frequency (band to the terminal station A
where any deterioration of the noise conditions of the
60 particular repeater station associated with the particular
received frequency band can be judged from the possibly
A. Checking 0n Ampli?cation and Aging
appearing increase of the received noise level.
EFrom the terminal station A the following auxiliary fre
It is of importance for the operation of the system ac
quencies f1 and f2 are transmitted and the corresponding
cording to the invention that the two carrier frequency
doubled modulation products or test frequencies 2]‘I are
bands and the intermediate frequency range therebetween
formed and received:
are so chosen that the frequencies amounting to twice the
value of all of the frequencies ‘located within the range
fL2—fL1 are located above the upper boundary of the
higher carrier frequency band and close to that boundary,
f1,
f2
(f+f2) =13,
2 f +f)=2 r,
Remarks
kc.
kc’.
1 kc.
( 1 k3. f
-70 in fact, if possible directly adjoining said upper boun
dary of the higher carrier -?'equency band because in this
Repeater:
case the total frequency band width can be kept Within
135
153
288
576
Received.
economical limits.
135
153 1
288. 1
576. 2
D0.
V1 has the test frequency f? :288.0 kilocycles
V2 has the test frequency $212881 kilocycles
V3 has the test frequency fT3:288.2 kilocycles
135
153 2
%8. 2
576. 4
D0.
It is always possible to arrange matters in such a man
75 ner that the amplitude or level of the modulation prod
Hi
9
1%
ucts received in the terminal stations is sut?ciently high
for furnishing an unequivocal indication of the perform
any speci?c one of said repeater stations from one of said
terminal stations toward the other terminal station will
form through superposition a test frequency which is dis
vtinctive of said speci?c one of said repeater stations and
located within said intermediate frequency range and
ance or operativeness of the respectively tested repeater
station, and this can the achieved by transmitting the above
mentioned auxiliary frequencies with a su?iciently high
amplitude. However, the level of the noise frequencies
will under normal conditions and operation of the re
therefore will be multiplied by the frequency-multiplier
means of that speci?c repeater station and returned to
said one terminal station through said transmission means
peater stations be located substantially below the obtain
provided that said speci?c repeater station is operating
able amplitude of the modulation products. In order to
improve the conditions for receiving the noise level and 10 properly.
2. In a carrier frequency communication system with
for increasing the sensitivity of modulation measurements
it is highly advisable to provide the frequency multipliers
two terminal stations and at least two intermediate two
in the various repeater stations according to the invention
not only with frequency-selective means as mentioned
above but also with a transistor ampli?er, the voltages and
Way repeater stations, operating with two separate car
currents required for its operation being available by
deriving them from the supply current.
It will be understood that each of the elements de
scribed above, or two or more together, may also ?nd a
useful application in other types of carrier frequency com
munication system di?wering from the types described
above.
While the invention has been illustrated and described
as embodied in a carrier frequency communication system
with two terminal stations and at least two intermediate
two-way repeater stations, operating with two separate
carrier frequency bands spaced from each other, it is
rier frequency bands spaced from each other, in combi
nation, two-conductor transmission means connecting in
tandem arrangement said terminal and repeater stations
for transmitting messages between said terminal stations
by means of a higher carrier frequency band in one
direction and of a lower carrier frequency band in the
opposite direction; each repeater station comprising ?rst
and second frequency-selective direction control means
connected between respectively adjoining portions of said
ransmission means for selectively passing said higher
and lower frequency bands, respectively, in said respec
tive directions, one-way ampli?er means having input
and output terminals, respectively, and being associated
with said direction control means for amplifying said
higher and lower frequency bands, respectively, and
not intended to be limited to the details shown, since
frequency-selective frequency-multiplier means connected
various modi?cations and structural changes may be made
without departing in any way from the spirit of the pres 30 between said output terminal and a junction point between
an adjoining portion of said transmission means and
ent invention.
that input end of said selective direction control means
Without further analysis, the foregoing will so fully
where said higher carrier frequency band is received,
reveal the gist of the present invention that others can by
for applying the output frequency band of said frequency
applying current knowledge readily adapt it for various
applications without omitting features that, from the stand 35 multiplier means to at least one of said ?rst and second
point of prior art, fairly constitute essential characteristics
direction control means, said frequency-multiplier means
of the generic or speci?c aspects of this invention and,
therefore, such adaptations should and are intended to
be comprehended within the meaning and range of equiv
alence of the following claims.
being capable of selectively multiplying only a discrete
What is claimed as new and desired to be secured by
Letters Patent is:
1. In a carrier frequency communication system with
two terminal stations and at least two intermediate two
test frequency band preassigned to and distinctive of the
particular repeater station and located within the inter
mediate frequency range between said higher and lower
carrier frequency bands and of delivering an output fre
quency higher than the lowest frequency of said higher
carrier band, ‘whereby two selected auxiliary frequencies
transmitted for testing any speci?c one of said repeater
way repeater stations, operating with two separate carrier 45 stations from one of said terminal stations toward the
other terminal station will form through superposition a
frequency bands spaced from each other, in combination,
test frequency band which is distinctive of said speci?c
two-conductor transmission means connecting in tandem
one of said repeater stations and located within said inter
arrangement said terminal and repeater stations for trans
mediate frequency range and therefore will be multiplied
mitting messages between said terminal stations by means
50
by the frequency-multiplier means of that speci?c repeater
of a higher carrier frequency band in one direction and
station and returned to said one terminal station through
of a lower carrier frequency band in the opposite direc
said transmission means provided that said speci?c re
tion; each repeater station comprising first and second fre
peater station is operating properly.
quency-selective direction control means connected be
tween respectively adjoining portions of said transmission
3. In a carrier frequency communication system with
means for selectively passing said higher and lower fre 55 two terminal stations and at least two intermediate two
Way repeater stations, operating with two separate car
quency bands, respectively, in said respective directions,
one~way ampli?er means having input and output termi
rier frequency bands spaced from each other, in combi
nals respectively, and 3being associated with said direction
nation, two-conductor transmission means connecting in
control means for amplifying said higher and lower fre
tandem arrangement said terminal and repeater stations
quency bands, respectively, and frequency-selective fre~ 60 for transmitting ‘messages between said terminal stations
by means of a higher carrier frequency band in one
quency-multiplier means connected between said output
terminal and a junction point between an adjoining por
tion of said transmission means and that input end of said
selective direction control means where said higher carrier
direction and of a lower carrier frequency band in the
frequency band is received, for applying the output
frequency'multiplier means being capable of selectively
multiplying only a discrete test frequency preassigned
connected between respectively adjoining portions of said
transmission means for selectively passing said higher
and lower frequency bands, respectively, in said respec
tive directions, single one-way ampli?er means having
input and output terminals, respectively, and being asso
quency of said higher carrier frequency band, whereby
two selected auxiliary frequencies transnutted for testing
an adjoining portion of said transmission means and
that input end of said selectivedirection control means
frequency of said frequency-multiplier means to at least
one of said ?rst and second direction control means, said
opposite direction; each repeater station comprising ?rst
and second frequency-selective direction control means
to and distinctive of the particular repeater station and 70 ciated with said direction control means for amplifying
located within the intermediate frequency range between
said higher and lower frequency bands, respectively,v and
said higher and lower carrier frequency bands and of de
frequency-selective frequency-multiplier means connected
livering an output frequency higher than the lowest fre
between said output terminal and a junction point between
3,049,596
1l
12
where said higher carrier frequency band is received,
for applying the output frequency of said frequency
tions by means of a higher carrier frequency band in
multiplier means to at least one of said ?rst and second
direction control means, said frequency-multiplier means
the opposite direction; each repeater station comprising
one direction and of a lower carrier frequency band in
?rst and second frequency-selective direction control
means connected between respectively adjoining portions
of said transmission means for selectively passing said
being capable of selectively multiplying only a discrete
test frequency preassigned to and distinctive of the par
ticular repeater station and located within the interme
diate frequency range between said higher and lower
carrier frequency bands and of delivering an output fre~
quency higher than the lowest frequency of said higher
higher and lower frequency bands, respectively, in said
respective directions, single one-way ampli?er means hav
ing input and output terminals, respectively, and being as
sociated with said direction control means for amplifying
carrier frequency band, whereby two selected auxiliary
said higher and lower frequency bands, respectively,
frequencies transmitted for testing any spcei?c one of
and frequency-selective frequency-doubling means con
nected between said output terminal and a junction point
between an adjoining portion of said ‘transmission means
toward the other tenminal station will form through super
position a test frequency which is distinctive of said 15 and that input end of said selective direction control
speci?c one of said repeater stations and located within
means where said higher carrier frequency band is re
said intermediate frequency range and therefore will
ceived, for applying the output frequency of said fre
be multiplied by the frequency-multiplier means of that
quency-doubling means to as least one of said ?rst and
speci?c repeater station and returned to said one terminal
second direction control means, said frequency-doubling
station through said transmission means provided that
means being capable of selectively doubling only a dis
said speci?c repeater station is operating properly.
crete test frequency preassigned to and distinctive of the
4. In a carrier frequency communication system with
particular repeater station and located within the inter
two terminal stations and at least two intermediate two
mediate frequency range between said higher and lower
carrier frequency bands and of delivering an output fre
way repeater stations, operating with two separate car
rier frequency bands spaced from each other, in com 25 quency higher than the lowest frequency of said higher
bination, two-conductor transmission means connecting
carrier frequency band, whereby two selected auxiliary
in tandem arrangement said terminal and repeater sta
frequencies transmitted for testing any speci?c one of
tions for transmitting messages between said terminal
said repeater stations from one of said terminal stations
stations by means of a higher carrier frequency band
toward the other terminal station will form through
said repeater stations from one of said terminal stations
in one direction and of a lower carrier frequency band in 30 superposition a test frequency which is distinctive of said
the opposite direction; each repeater station comprising
speci?c one of said repeater stations and located within
said intermediate frequency range and therefore will be
doubled by the frequency-doubling means of that spe
ci?c repeater station and returned to said one terminal
higher and lower frequency bands, respectively, in said 35 station through said transmission means provided that said
?rst and second frequency-selective direction control
means connected between respectively adjoining portions
of said transmission means for selectively passing said
speci?c repeater station is operating properly.
respective directions, one-way ampli?er means having in
put and output terminals, respectively, and being asso
6. In a carrier frequency communication system with
two terminal stations and at least two intermediate two
ciated with said direction control means for amplifying
said higher and lower frequency bands, respectively, and
frequency-selective frequency doubling means connected
40
way repeater stations, operating with two separate carrier
frequency bands spaced from each oher, in combination,
between said output terminal and a junction point be
tween an adjoining portion of said transmission means
and that input end of said selective direction control
means where said higher carrier frequency band is re
two-conductor transmission means connecting in tandem
arrangement said terminal and repeater stations for trans
mitting messages between said terminal stations by means
of a higher carrier frequency band in one direction and
ceived, for applying the output frequency of said fre 45 of a lower carrier frequency band in the opposite direc
quency-doubling means to at least one of said ?rst and
tion; each repeater station comprising ?rst and second
‘frequency-selective direction control means connected be
second direction control means, said frequency-doubling
means being capable of selectively doubling only a dis
tween respectively adjoining portions of said transmission
means for selectively passing said higher and lower fre
crete test frequency preassigned to and distinctive of the
particular repeater station and located within the inter 50 quency bands, respectively, in said respective directions,
one-way ampli?er means having input and output termi
mediate frequency band between said higher and lower
nals, respectively, and being associated with said direc
carrier frequency bands and of delivering an output fre
tion control means for amplifying said higher and lower
quency preassigned to and distinctive of the particular
frequency bands, respectively, and frequency-selective
repeater station and located within the intermediate fre
frequency-multiplier means connected between said out
quency range between said higher and lower carrier
put terminal and a junction point between an adjoining
frequency bands and of delivering an output frequency
portion of said transmission means and that input end of
higher than the lowest frequency of said higher carrier
said selective direction control means where said higher
frequency band, whereby two selected auxiliary frequen
carrier frequency band is received, for applying the out
cies transmitted for testing any speci?c one of said repeater
put frequency of said frequency-multiplier means to at
stations from one of said terminal stations toward the
least one of said ?rst and second direction control means,
other terminal station will form through superposition a
said frequency-multiplier means being capable of selec
test frequency which is distinctive of said speci?c one
tively multiplying only a discrete test frequency pre
of said repeater stations and located within said inter
assigned to and distinctive of the particular repeater sta
mediate frequency range and therefore will be doubled
by the frequency-doubling means of that speci?c repeater 65 tion and located within the intermediate frequency range
between said higher and lower carrier frequency bands
station and returned to said one terminal station through
‘and of delivering an output frequency higher than the
said transmission means provided that said speci?c re
peater station is operating properly.
lowest frequency of said higher carrier frequency band;
5. In a carrier frequency communication system with
two terminal stations and at least two intermediate two
way repeater stations, operating with two separate car
a supplementary frequency higher than the lowest fre
quency of said higher carrier frequency band, for mixing
rier frequency bands spaced from each other, in combi
said supplementary frequency with said output frequency
and means for introducing into said transmission means
end for producing a modulation product having a fre
nation, two-conductor transmission means connecting in
tandem arrangement said terminal and repeater stations
quency located within said lower carrier frequency band,
for transmitting messages between said terminal sta 75 whereby two selected auxiliary frequencies transmitted
3,049,596
23
for testing any speci?c one of said repeater stations from
one of said terminal stations toward the other terminal
station will form through srper-position a test frequency
which is distinctive of said speci?c one of said repeater
station will form through superposition a test frequency
range and therefore will be multiplied by the frequency
multiplier means of that speci?c repeater station and
mixed with said supplementary frequency, and said modu
lation product will be returned to said one terminal sta
tion through said transmission means provided that said 10
speci?c repeater station is operating properly.
iii
rections, one-way ampli?er means having input and out
put terminals, respectively, and being associated with said
direction control means for amplifying said higher and
lower frequency bands, respectively, and frequency-selec
tive frequency-doubling means connected between said
output terminal and a junction point between an ad—
joining portion of said transmission means and that in—
put end of said selective direction control means where
said higher carrier frequency band is received, for apply
ing the output frequency of said frequency-doubling
means to at least one of said ?rst and second direction
control means, said frequency-doubling means being ca
7. In a carrier frequency communication system with
two terminal stations and at least two intermediate two
pable of selectively doubling only a discrete test frequency
preassigned to and distinctive of the particular repeater
way repeater stations, operating with two separate carrier
frequency bands spaced from each other, in combination, 15 station and located within the intermediate frequency
range between said higher and lower carrier frequency
two-conductor transmission means connecting in tandem
bands and of delivering an output frequency higher than
arrangement said terminal and repeater stations for trans
the lowest frequency of said higher carrier frequency
mitting messages between said terminal stations by means
band; and means for introducing into said transmission
of a higher carrier frequency band in one direction and
of a lower carrier frequency band in the opposite direc
20 means a supplementary frequency higher than the lowest
frequency of said higher carrier frequency band, for mix
ing said supplementary frequency with said output fre
tion; each repeater station comprising ?rst and second
frequency-selective direction control means connected be
quency end for producing a modulation product having a
frequency located within said lower carrier frequency
tween respectively adjoining portions of said transmission
means for selectively passing said higher and lower fre
quency bands, respectively, in said respective directions, 25 band, whereby two selected auxiliary frequencies trans
mitted for testing any speci?c one of said repeater sta
single one-way ampli?er means having input and output
tions from one of said terminal stations toward the other
terminals, respectively, and being associated with said
terminal station will form through superposition a test
direction control means for amplifying said higher and
frequency which is distinctive of said speci?c one of said
lower frequency bands, respectively, and frequency-selec
tive frequency-multiplier means connected between said 30 repeater stations and located within said intermediate
frequency range and therefore will be doubled by the
output terminal and a junction point between an adjoining
frequency-doubling means of that speci?c repeater sta
portion of said transmission means and that input end
tion and mixed with said supplementary frequency, and
of said selective direction control means where said higher
said modulation product will be returned to said one ter
carrier frequency band is received, for applying the out
put frequency of said frequency-multiplier means to at 35 minal station through said transmission means provided
that said speci?c repeater station is operating properly.
least one of said ?rst and second direction control means,
said frequency-multiplier means being capable of selec
9. In a carrier frequency communication system with
tively multiplying only a discrete test frequency preas
two terminal stations and at least two intermediate two
way repeater stations, operating with two separate car
signed to and distinctive of the particular repeater station
and located within the intermediate frequency range be 40 rier frequency bands spaced from each other, in com
tween said higher and lower carrier frequency bands and
bination, two-conductor transmission means connecting
of delivering an output frequency higher than the lowest
in tandem arrangement said terminal and repeater sta
frequency of said higher carrier frequency band; and
tions for transmitting messages between said terminal sta
tions by means of a higher carrier frequency band in one
direction and of a lower carrier frequency band in the
means for introducing into said transmission means a
supplementary frequency higher than the lowest frequency
of said higher carrier frequency band, for mixing said
supplementary frequency with said output frequency end
opposite direction; each repeater station comprising ?rst
and second frequency-selective direction control means
connected between respectively adjoining portions of said
for producing a modulation product having a frequency
located within said lower carrier frequency band, whereby
two selected auxiliary frequencies transmitted for testing
transmission means for selectively passing said higher and
any speci?c one of said repeater stations from one of said
terminal stations toward the other terminal station will
form through superposition a test frequency which is
distinctive of said speci?c one of said repeater stations
and located within said intermediate frequency range and 55
therefore will be multiplied by the frequency-multiplier
lower frequency bands, respectively, in said respective di
rections, single one-way ampli?er means having input
and output terminals, respectively, and being associated
with said direction control means for amplifying said
higher and lower frequency bands, respectively, and fre
quency-selective frequency-doubling means connected be
said supplementary frequency, and said modulation prod
tween said output terminal and a junction point between
an adjoining portion of said transmission means and that
input end of said selective direction control means where
uct will be returned to said one terminal station through
said transmission means provided that said speci?c re
said higher carrier frequency band is received, for ap
plying the output frequency of said frequency-doubling
eans of that speci?c repeater station and mixed with
peater station is operating properly.
means to at least one of said ?rst and second direction
8. In a carrier frequency communication system with
two terminal stations and at least two intermediate two
control means, said frequency-doubling means being ca
way repeater stations, operating with two separate carrier
frequency bands spaced from each other, in combina
tion, two-conductor transmission means connecting in
tandem arrangement said terminal and repeater stations
for transmitting messages between said terminal stations
by means of a higher carrier frequency band in one di
rection and of a lower carrier frequency band in the op
posite direction; each repeater station comprising ?rst
pable of selectively doubling only a discrete test fre
quency preassigned to and distinctive of the particular
repeater station and located within the intermediate fre
quency range between said higher and lower carrier fre
quency bands and of delivering an out-put frequency higher
than the lowest frequency of said higher carrier frequency
band; and means for introducing into said transmission
70 means a supplementary frequency higher than the lowest
frequency of said higher carrier frequency band, for mix
ing said supplementary frequency with said output fre
connected between respectively adjoining portions of said
quency end for producing a modulation product having
transmission means for selectively passing said higher and
a frequency located within said lower carrier frequency
lower frequency bands, respectively, in said respective di 75 band, whereby two selected auxiliary frequencies trans
and second frequency-selective direction control means
3,049,596
15
16
mitted for testing any speci?c one of said repeatersta~
said modulation product will be returned to said one ter
tions from one of said terminal stations toward the other
terminal station will form through superposition a test
frequency which is distinctive of said speci?c one of said
that said speci?c repeater station is operating properly.
repeater stations and located within said intermediate 5
frequency range and therefore will be doubled by the
frequency-doubling means of that speci?c repeater sta
tion and mixed with said supplementary frequency, and
minal station through said transmission means provided
References Cited in the ?le of this patent
UNITED STATES PATENTS
Cameron ____________ __ Feb. 11,
2,823,270
1958
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