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Патент USA US3045123

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July 17, 1962
R. c. FERRAR Erm.
FAULT LOCATION SYSTEM
Filed NOV. 16, 1959
A
' 3,045,113
13a-talla
United States Patery O ”"¿Ce
Patented July 17, 1962V
l
2
3,045,113
communication systems overcoming the above-mentioned
disadvantages of the` prior art fault location systems.
Robert C. Ferrar, Glen Ridge, and Ross B. Hoffman,
Another object of this invention is to provide a fault lo
cation system which overcomes the disadvantages of the
FAULT LOCATION SYSTEM
Highlands, NJ., assignors to International Telephone
and Telegraph Corporation, Nutley, NJ., a corporation
of Maryland
first-mentioned prior art fault location system utilizing
la greatly reduced amount of additional equipment in com
parison to that employed in the second-mentioned prior
Filed Nov. 16, 1959, Ser. No. 3,703
20 Claims. (Cl. 325-2)
art fault location system.
»
A feature of this invention is the provision of-a source
This invention relates to communication systems and 10 of signals having a given frequency coupled to a fre
more particularly to a communication system having
means to rapidly localize equipment that has failed in
quency converting means of a receiver in the absence of
an output signal from the receiver toY simulate a signal
having the normal output frequency of the frequency con
verting means to determine the operating condition of the
line-of-sight types or over-the-horizon types is to be able 15 receiver.
' Another feature of this invention is the provision of a
to define which component of the system has failed in
station including a transmitter and a receiver coupled by
order to allow either rapid automatic change to standby
means of a duplexer to a _single antenna and an oscil
equipment or to rapidly localize the fault toa particular
lator generating an output signal having a frequency equal
station. A major obstacle has been the inability in a
communication system containing a transmitter and a re 20 to the difference between the transmit and receive carrier
frequencies and a means to couple the output signal of
ceiver to deñne which of these components has failed.
the oscillator to the heterodyning means included in said
One prior art fault locating system follows the follow
receiver in the absence of -output signals from said re
ing technique. Upon the failure of receiving a signal
ceiver to simulate in conjunction with the leakage of the
at the receiver, the switching of regular equipment to 'the
standby equipment is delayed after a receiver output loss 25 output signal of said transmitter through said duplexer
a signal having the normal intermediate frequency at the>
for about fifteen seconds in order to allow the trans
output of said heterodyning means to thereby provide an
mitter at the adjacent station to switch from regular equip
indication of whether said receiver or the transmitter of
ment to standby equipment. If there is still no signal
an adjacent station include the faulty equipment by
after this interval, the receiver switches to standby equip
ment. lf a signal is then received, the standby equipment 30 whether or not said simulated signal produces a receiver
would remain in service and it would be known that the
Still another feature of this invention is the provision
regular receiver equipment had failed. lf no signal were
of an arrangement,as outlined above, in each station of'
received, the regular receiver equipment is returned to
said communication system.
A problem in communication systems including both
output.
I
'
'~
,
a multistation communication system and a remote con
service and remains in an operative condition until serv
ice is restored and then another failure occurs. The 35 trol selcctive system operated from one station whereby
the oscillators are sequentially controlled to inject their
output signal into the heterodyning means of their asso
ciated receiver proceeding sequentially from said one sta
tion until such time that the simulated signal in the com
to standby equipment. The‘weaknesses and disadvantages
of this system are (l) long switchover time due to re 40 munication system is not returned to the receiver of said
one station thereby indicating the station that contained
ceiver delay, (2) the possibility of standby or switching -
switching back to the' regular equipment in the receiver
would indicate that the transmitter had failed a‘nd that the
switching equipment had failed to transfer the transmitter
failure creating another fault, and (3) the possibility of
the faulty equipment.
switching to standby being unnecessary if return to service
of distant station coincided with standby receiver sam
The above-mentioned and other features and objects
of this invention and the manner of obtaining them will`
-
pling.
become more apparent by reference-to the following de
Another prior art fault locating system particularly use
ful for two-way communication systems includes a crystal
mixer disposed between the transmitter output and re
ceiver input with suflicient decoupling to reduce the ’trans
drawing, the single FIGURE of which illustrates a sche
matic diagram in block form of a Ifault location system
scription taken in conjunction with the accompanying
following the principles of this invention.
50
Referring to the FIGURE, there is illustrated therein a
mitter level at the receiver to a value about that nor
communication system employing the fault location sys
mally received. An oscillator is provided having a sig
tem of this invention. The communication system is i1
nal ata frequency equal to the difference between the
transmitter and receiver carriers frequencies which is in
jected into the added crystal mixer to thereby coact with
the transmitter signal to simulate the receipt ~of a signal
from the distant transmitter. Through this method it can
be determined by a process of elimination whether the
lustrated as including terminal station 1, terminal station
2 and a plurality of repeater stations 3 and 4 disposed
intermediate terminal station 1 and terminal station 2¿.
Although only two repeater stations are illustrated the
communication path between terminal stations 1 and'Z
may include any necessary number of repeater stations. '
The communication system illustrated is a two-way com-_
receiver or transmitter in the communication link has
failed.
If the simulated signal passes through the re
60
munication system of the line-of-sight type with intel
ceiver to its output then there is good reason to believe
ligence being transmitted on a carrier frequency F1 from
that the receiver is operating and that the distant trans
terminal station 1 to terminal station 2 and with intellif/ ~ '
' mitter has failed. If the receiver does not pass the simu
lated signal to its output there is then good reason to be
lieve that the receiver has failed. While this arrangement
eliminates the three disadvantages above outlined there
,gence being transmitted on a carrier frequency F2 froml
terminal station 2 to terminal station 1.
While the fault location system of this invention is il- '
lustrated in conjunction with a line-of-sight type coni
munication system, it is to be understood that the tech- 'e y
is required the addition of transmission lines, decoupling
niques taught herein can be employed also with over-thc
means, mixer cavities and mixer crystals to provide the
horizon type communication systems.
.
simulated signal at the receiver input.
'I'he additional components and their cooperative rela
70
Therefore, an object of this invention is to provide an
improved fault location system for employment with
tionship with certain of the regular components of` a corn- - -
munication system to provide the improved fault location
3,045,113
4
3
system of this invention are illustrated in detail in repeater
station 3 in connection with receiver 7 and terminal sta
tion 1. Brietiy and in general terms the additional com
ponents include a test oscillator generating a signal having
a given frequency and a control circuit coupled thereto
to control the coupling of the output signal from the test
oscillator to the receiver with which these components
are associated, namely, the receivers of each station. In
accordance with the detail of station 3, test oscillator 5
and control circuit 6 are associated with receiver 7. Simi
lar components identified in the drawing as test oscillator
and control circuits 8, 9 and 10 are illustrated to be, re
spectively, associated with receiver 11 of station 1, re
ceiver 12 of station 2 and receiver 13 of station 3. Al
though repeater station 4 is not shown in any detail what
soever itis to be understood that repeater station 4 will in
clude substantially the same equipment as that included in
repeater station 3.
The control circuits, such as control circuits 6, may be
Operated at its associated station by an operator to couple
the output of the test oscillator, such as oscillator 5, to
their associated receiver, such as receiver 7, upon loss of
output signals from the associated receiver to determine
whether the receiver 7 has failed or the transmitter from
which receiver 7 receives its signal has failed. Since 25
there may be a number of repeater stations, such as re
peater stations 3 and 4, and these stations may be unat
associated test oscillator, such as oscillator 5. With each
control circuit responding to a different frequency, selec
tive calling techniques may be employed to sequentially
activate the test oscillator in each of the stations proceed
ing from the receiving end of a communication direction
to the transmitting end thereof as described above. Con
trol circuit 6 may be, if operated on a one-hop communi
cation system, such as an over-the-horizon communica
tion system, or in an attended station of a multi-station
line-of-sight communication path, a manually operated
switch which an operator would activate to inject the out
put signal of the test oscillator into the associated re
ceiver. In either case, remote control or local control, the
switch may be in the output signal lead or it may be in the
power supply lead of the oscillator. In the latter situation,
it would be advisable to have the filament power “on” at
all times and to switch the anode power lead. This main
tains the oscillator in a ready condition and eliminates the
time required for warmup lif the filament power were
switched along with the anode power.
yHaving discussed the added components and a certain
amount of the operation thereof, particularly with respect
to the control circuits activating the test oscillators, we
will now deal with the components of the regular com
munication system with which the added components of
the fault location system of this invention cooperate. The
remaining description will be directed toward repeater
stations 3 wherein the detail of the regular communica
tended, some means must be provided to enable an oper
tion system components are illustrated in a cooperative
ator at a terminal station to localize the equipment that
has failed in a particular direction of communication on 30 relationship with test oscillator 5 and control circuit 6.
the communication path. This may be accomplished by
resorting to remote control techniques wherein it is pos
sible for an operator at say terminal station 1 to sequen
tially activate the control circuits associated with the re
ceivers in the direction of communication being received
at this terminal station. Hence, if there is no output in
utilization device 14 of receiver 11, an opera-tor would
activate a tone generator and selector 15 to cause appro
priate tone signals to be coupled via transmission lines,
such as telephone lines, to the control circuits of each re
ceiver in this particular direction of communication. For
instance, the operator would activate test oscillator 8 by
depressing a button in tone generator and selector d5 so
designated to activate test oscillator 8. If simulated sig
nals are recognized in utilization means 14, the operator
then knows that it is equipment succeeding receiver 11,
going from terminal 1 to terminal 2, which has failed and
he, therefore, presses the appropriate button to activate
the test oscillator in the next adjacent station, such as test
oscillator S in station 3. Recognition of the simulated
signals at utilization means 14 indicates that the failed
equipment is further along this communication path to
ward terminal 2. This sequential energization of the con
trol circuits associated with succeeding repeater stations
enables the operator to determine which of the stations in
cludes the faulty equipment since there will be no simu
lated signal output at device 14 when the test oscillator
has been energized in the station where the faulty equip
ment is located. Having now localized the fault, it is pos
sible to quickly switch the transmitter and receiver se
quentially tostandby equipment to determine which of
the equipments had failed and to reinstate communica
tion in this particular direction of communication, namely,
from terminal 2 to terminal 1 in the present illustration.
Localization of faulty equipment may be accomplished as
described above for the direction of communication from
terminal station 1 to terminal station 2 by employing tone
generator and selector 16 and test oscillators and control
circuits 9 and 10. The control circuit, such as control
circuit 6, may be any number of well known types of se
lector and/ or switch circuits.
In a remote control situa
tion, circuit 6 may include a circuit tuned to a particular
The regular communication system equipment neces
sary for the operation of this fault location system is a
duplexer 17 including a transmit filter 18 and a receive
filter 19 and a frequency converting -means 20 to con
vert the received carrier frequency, such as F2, in the
communication direction from terminal station 2 to ter
minal station 1 to another frequency which will enable
the receiver to have an output signal, either for ener
gization of an intelligence recovering device or for cou
pling to the transmitter of the repeater station, such as
transmitter 21 of repeater station 3. This frequency
converting means could be a parametric amplifier where
in the received signal at F2 is raised in frequency and
amplitude to provide a signal output having a predeter
mined frequency which may then be operated upon by
succeeding circuitry to produce a useful output signal
from the receiver 7. It will then be necessary for test
oscillator 5 to produce a signal having a given frequency
which through cooperation with frequency converting
means 20 simulates the output of the parametric ampli
fier thereby enabling a testing of the components and
equipment in the repeater or terminal station in accord
ance with the principles of this invention. For purposes
of explanation, however, the operation of the fault -loca
tion system of this invention is described utilizing a
heterodyning means 22 as frequency converting means
20. Means 22 includes local oscillator 23 and mixer
24. The resultant output of mixer 24 is the usual IF
(intermediate frequency) signal produced in a super
60 heterodyne receiver which is lower than the received car
rier frequency. The resultant output of the mixer, the
IF signal, is coupled to an IF amplifier and succeeding
circuitry 25 with the output thereof being coupled to
transmitter 21 for `application to duplexer 26 and hence,
F reception at terminal station 1 for application to receiver
11 for utilization in device 14.
lt should be pointed out that in repeater stations,
such as repeater station 3, the signal at the output of
receivers therein, such as receivers 7 and 13 may be
coupled to the transmitter associated with that particu
lar communication direction at an IF frequency or an
audio frequency depending upon the operation of the
repeater. The frequency at which the signal is coupled
frequency is selected by the operator, the tuned circuit willrespond thereto operating a switch for activation of its 75 from, say receiver 7 to transmitter 21 does not play a «
frequency. When the tone signal having said particular
3,045,113
5
role in the fault location system of this invention. All
ing energy on antenna 27 is produced -by the following
that is necessary is -that a useful output be provided
frequencies:
at the output of the receivers if they are operating. This
useful output could be either |at an 1F level or an audio
level depending upon whether they are in a repeater
station or a terminal station and whether in the repeater
station the signals are coupled at an IF or audio level
’
F1-FL0-FT=F1--FL0--(F1--F2)
=F2--FL0=F2-F2+F0=F0
Thus, through the cooperation of `the signal generated
in oscillator 5, the leaking signal from transmitter Z8
and the output of local oscillator 23, it is possibleto>
»to the succeeding transmitter in the communication di
produce at the output of mixer 24 a simulated inter
rection.
For a more complete understanding of the operation 10 mediate frequency F0 which will produce a simulated
signal at the output of receiver 7 and hence, through the
0f the fault location system of this invention the follow
remainder of the communication system ,to the receiver _
ing discussion is presented with reference to the com
11 included in terminal station 1 if the intervening com
munication direction on the communication path from
ponents of the communication direction are in operation.
terminal station 2 to terminal station land with par
It can then be stated that upon failure in a communicta
ticular reference to the detail circuitry shown in repeater 15
tion hop including at least a receiver and transmitter the
station 3 in connection with receiver 7. During normal
energization of the test oscillator will provide a simulated
yoperation 4a signal Ihaving a frequency F2 is received on
intermediate frequency signal at the output of the
antenna 27 from repeater station 4 and is coupled by
heterodyning means for coupling to the output of the re
means of receiving filter 19 of yduplexer 17 to mixer 24.
The output signal of local oscillator 23 having a fre 20 ceiver, if the receiver is operating. Hence, if a simulated
signal appears at the outputof the receiver this is »an in
quency equal to FL0=F2-F0 is also coupled to mixer
dication that the receiver equipment has not failedV and
24. The frequency of the resultant output signal of
that actually the transmitter equipment h-as failed.
mixer 24 is an intermediate frequency,y F0.
Utilizing a similar approach »and remote control
Let us vassume that the transmitter transmitting to re-r
ceiver 7 has failed. This failure of course results in no 25 techniques to control the operation of the test oscillator
it would be possible to localize the station in a multi-sta
output signal `from receiver 7 and utilization device 14.
tion communication system that contained the equipment
Under this condition the frequency of the output signal
that caused loss of communication. The technique is as
`of mixer 24 will be F1-FL0=(F1-F2)-l-F0. The fre
follows: Assume no output from utilization device 14
quency F1 enters into the signal output of mixer 24 in
which indicates a failure has occurred in the communica
the absence of signal F2 at antenna 27, since it is well
tion direction from .terminal station 2 to terminal station
known there is a certain amount of leakage through
1. The operator energizes the appropriate tone ¿for
duplexer 17 from transmitter 28 to mixer 24. With
coupling from generator 15 to test oscillator 8 of termi
this output upon the failure of receiving signal F2 at
nal station 1. Assume that a simulated output signal
Iantenna 27, the IF amplifier at succeeding circuitry 25
appears in utilization device 14. It is true that this may
Will not be able to function since the `output frequency
be a very Weak signal -but it will be one which the opera
of mixer 24 is not proper, namely the output frequency
-tor will be able to observe. The output from receiver 11
of mixer 24 is not Fò'f This loss of signal at antenna 27
indicates that receiver (11 is operating `and that it is equip-would of course he reflected by a lack of output from
ment succeeding receiver 11 traveling from the terminal
Ireceiver 7 in the case of only a single hop communica
station 1 to the terminal station 2, the direction in which
tion system and also in the case of a multi-hop communi
the stations are sequentially tested by remote control from
cation -system no signal youtput, would be present at uti
ltone generator and selector 15. Having received output
lization device 14. The loss of signal would indicate to
from receiver 11 the operator would next energize the
an operator to activate the control circuit 6, either by
test oscillator 5 of repeater station 3 to determine whether
remote »operation through tone generator and selector 15,
or by a local operation, if it is an attended station, to
caus'e'the injection of the output signal of test oscillator
5 into mixer 24. With the presence of leakage of fre
a simulated output is now received at receiver 11.
As
suming that an output is received at receiver 11 when test
oscillator 5 is energized, the operator then knows that
quency F1 through duplexer 17 from transmitter 28, the
output signal of test oscillator 5, indicated as FT is equal
repeater station 3 is operable and that the faulty equip~
signal transmitted by transmitter 28, the frequency of
into operation. The transmitter could be switched to
ment is not contained in this repeater station. The
to (F1-F2), a frequency equal to the difference between 50 operator will then next energize the test oscillator con
tained in repeater station 4. Assume that there is no
the carrier frequencies of the signals traveling in oppo
signal received at receiver 11. .Y This would indicate to
site directions on the communication path between ter
the operator that repeater station 4 contains the Ifaulty
minals 1 and 2. lt is to be remembered, however, that
equipment. Action would then be taken to quickly switch
the frequency of the signal at the output of test oscil
lator 5 would be adjusted to meet the conditions present 55 the equipment of repeater station 4 sequentially to standby'
equipment to place this communication direction back
in lthe receiver. Hence, if there were no leakage of the
standby equipment and if service was restored, it is cer- ,
tain «that the transmitter was at fault. ~ If, however, service
was not restored, the probability that the receiver is at
nal output of the local oscillator 23. _With or without 60
the signal at the output of test oscillator 5 would have
to be changed with respect to the «frequency of the sig
fault is very high. The receiver is then switched to stand
by and service will more than likely bey restored.
would have to be adjusted in frequency to produce lthe
Hereinabove we have described the techniques of fau-lt.
desired output signal 'from frequency converting means
location employing the components of this invention in
20 to cause a simulated output signal from receiver 7
addition to the regular communication system components
with the loss of signal at frequency F2, if a parametric 65 with respect to the communication direction between
-signal leakage tfrom transmitter 28, the output signal
amplifier were utilized yas frequency converting means 20.
terminal station 2 yand 'terminal station 1.,v A similar ~ar-
Upon energization of test oscillator 5 through the op
eration of control circuit 6, the output signal of test
rangement -and procedure may be employed in ,conjunc
tion with the test oscillator and control circuits 9 and
oscillator 5 at a frequency FT is coupled to «mixer 24. 70 10 »and tone generator land selector 16 for remote con-trol
in the communication direction from Yterminal station 1 to
When this signal is mixed with ythe youtput of local os
cillator 23 andthe signal leaking through duplexer 17
terminal station 2.
from transmitter 28, there results at the output ofV mixer
24 a simulated signal at a frequency F0. This simulated
It can be shown for the communication direction from
terminal 1 to terminal 2 that upon normal operation the
.
»
'
signal at the output of mixer 24 upon failure of receiv 75 frequency of the output signal of the receiver mixer-is
3,045,113
F0’=F1-FL0’. Upon failure of a transmitter transmitting
signals to the receiver, the output signal of the receiver
mixer, such las in receiver 13, would have a frequency equal
to F2-FL0’= z-FH-Fo’. When the test oscillator
is turned on either by a local activation thereof or
by remote control selection and activation thereof from
tone generator 16, the output signal therefrom at a fre
quency FT'=F2-F1 produces at the output of the receiver
mixer the normal output F0’ which is obtained by
heterodyning the following frequency signal:
The system above described for localizing a particular
component of a communication system including a single
transmitter and a receiver which has failed, or localizing
a particular station that includes the failed equipment
has the advantage over the ñrst mentioned prior art ar
rangement in that it is rapid and positive in operation
similar to the second mentioned prior art arrangement.
The present invention has an improvement over the sec
ond mentioned prior art arrangement in that only the
addition of a simple test oscillator and an arrangement
to inject the output of the test oscillator into the frequency
converting or heterodyning arrangement of the receiver
is necessary.
This is in contrast to the second mentioned
prior art arrangement which required transmission lines
and decoupling means for connecting the added mixer
cavity and mixer crystal between the transmitter and
receiver operating in opposite communication directions,
signals having a given frequency associated with said
heterodyning means, and controllable means to inject
the signal of said source of signals into said heterodyning
means in the absence of said output signal to simulate at
the output of said heterodyning means a signal having
said intermediate frequency to determine the operating
condition of said receiver.
4. A fault locating system for communication systems
comprising a plurality of transmitters and receivers alter
nately arranged in tandem to provide a continuous com
munication path for communication by a signal at a given
carrier frequency, each of said receivers including a
heterodyning means to convert the signal having said
given carrier frequency to a signal having a given inter
mediate frequency to provide an output signal from its
associated one of said receivers when said associated re
ceiver is operating, a source of signals having a given fre
quency associated -with each of said heterodyning means,
and controllable means to inject the signals of said source
of signals into its associated one of said heterodyning
means in the absence of said output signal from said asso
ciated receiver to simulate at the output of said hetero
dyning means a signal having said intermediate frequency
to determine the operating condition of said associated
receiver.
5. A fault locating system for communication systems
comprising a terminal station at each end of a communi
cation path, a plurality of repeater stations disposed in
termediate said terminal stations, each of said repeater
for instance between transmitter 28 and receiver 7, yas 30 stations include both a transmitter and receiver, one of
said terminal stations includes la receiver and the other
well as a test oscillator to enable the simulation of a signal
of said terminal station includes a transmitter to cooper
at the input of the receiver equal in frequency to the usual
ate in providing communication by a signal at a given
received carrier frequency. The system of this invention
carrier frequency, each of said receivers including a
has an advantage over the prior art arrangements in .that
the equipment added to the regular communication system
equipment is relatively inexpensive as compared with
the added equipment of the prior art arrangements.
While we have described above the principles of our
invention in connection with speciñc apparatus, it is to
be clearly understood that this description is made by way
of example and not as a limitation to the scope of our
invention as set forth in the objects thereof and in the
accompanying claims.
We claim:
l. A fault locating system for communication systems
comprising a receiver Ifor receiving a signal having a
given carrier frequency from a distant transmitter, said
receiver including a means to convert the signal having
said given carrier frequency to a signal having a predeter
mined frequency to provide an output signal from said
receiver when said receiver is operating and a source of
signals having a given frequency coupled to said con
verting means in the absence of said output signal to
simulate at the output of said converting means a signal
having said predetermined frequency to determine the
operating condition of said receiver.
heterodyning means to convert the signal of said given _
carrier frequency to a signal having a given intermediate
frequency to provide an output signal from its associated
one of said receivers when said associated receiver is
operating, a source of signals having «a given frequency
associated with each of said heterodyning means, and
controllable means coupled to each of said source of sig
nals selectively operated from said one terminal to sequen
tially inject the signals of each of said sources of signals
into their associated one of said heterodyning means in the
absence of output signal from the receiver of said one
terminal to simulate at the output of said heterodyning
means associated with said selected source of signals a
signal having said intermediate frequency to sequentially
determine the operating condition of each of said receivers
until the fault is localized to a particular station.
6. A fault locating system for communication systems
comprising a station including a transmitter `for trans
mitting a signal to a distant receiver at a first frequency,
a receiver for receiving a signal from a distant trans
mitter at a second frequency, an antenna, means coupling
said antenna to said transmitter and said receiver, said
receiver including a means to convert the signal at said
2. A fault locating system for communication systems
second frequency to a signal having a predetermined
comprising a receiver for receiving a signal having a
frequency to provide an output signal `from said receiver
given carrier frequency from a distant transmitter, said
when said receiver is oper-ating, and an oscillator gen
receiver including a heterodyning means to convert the 60 erating an output signal having a given frequency coupled
signal having said given carrier frequency to a signal hav
to said converting means in the absence of said output
ing la given intermediate frequency to provide an output
signal to simulate in conjunction with the leakage of sig
signal from said receiver when said receiver is operating
nal of said ñrst frequency through said antenna coupling
and a source of signals having a given frequency coupled
means into said converting means a signal vhaving said
to said heterodyning means in the absence of said out
predetermined frequency to determine the operating con
put signal to simulate at the output of said heterodyning
dition of said receiver.
means a signal having said intermediate frequency to de
7. A `fault locating system for communication systems
termine the condition of said receiver.
comprising a station including -a transmitter for trans
3. A fault locating system 4for communication systems
comprising a receiver for receiving a signal having a given 70 mitting a signal to a distant receiver at a first frequency,
a receiver for receiving a signal from a distant transmitter
frequency from a distant transmitter, said receiver in
at
a second frequency, an antenna, means coupling said
cluding a heterodyning means to convert the signal hav
antenna to said transmitter and said receiver, said re
ing said given carrier frequency to a signal having a given
ceiver including a heterodyning means to convert the sig
inter-mediate frequency to provide an output signal from
nal at said second frequency to a signal having a given
said receiver when said receiver is operating, a source of
3,045,113
9
.
intermediate frequency to provide an output signal from
10
t
~
-
to inject the output signal of said oscillator into said
said receiver when said receiver is operating, and an
heterodyning means in the absence of saidv output signal
oscillator generating an output signal having a given fre
` to simulate in conjunction with the leakage of signal of
said first frequency through said antenna coupling means
into said heterodyning means a signal having said inter
quency coupled to said heterodyning means in the absence
of said output signal to simulate in conjunction with the
leakage of signal of said first frequency through said an
tenna coupling means into said heterodyning means a sig
nal having said intermediate frequency to determine the
operating condition of said receiver.
8. A fault locating vsystem for communication systems
comprising a station including a transmitter for trans
mitting a signal to a distant receiver at a first frequency,
a receiver for receiving a signal from a distant transmitter
at a second frequency, an antenna, means coupling said
antenna tol said transmitter and said receiver, said receiver
mediate frequency to determine the operating condition
of said receiver.
12. A fault locating system for communication systems v
comprising a station including a transmitter for transmit
ting a signal to a distant receiver at a Ifirst frequency, a
receiver for receiving a signal from a» distant transmitter
at a second frequency, an antenna, means coupling said
antenna to said transmitter and said receiver, said re
ceiver including a heterodyning means to convert the sig
nal -at said second frequency to a signal having a given `
including a heterodyning means -to convert the signal at
intermediate frequency to provide an output signal from
said second frequency to a signal having a -given inter
said receiver when said receiver is operating, an oscillator
mediate frequency to provide an output signal from said
generating an output signal having a frequency equal to
receiver when said receiver is operating, and an oscillator
the difference between said first and second frequencies
generating an output signal having a frequency equal to 20 associated with said heterodyning means, and controllable
the difference between said first and second frequencies
means to inject the output signal of said oscillator into
coupled to said heterodyning means in the absence of
said heterodyning means in the absence of said output
said output signal to simulate in conjunction with the
signal to simulate in conjunction with the leakage of sig
leakage of signal of said first frequency through said an
nal of said first frequency through said antenna coupling
tenna coupling means into said heterodyning means a sig
means into said heterodyning means »a signal having said
nal having said intermediate frequency to determine the
intermediate frequency to determine the operating condi
operating condition of said receiver.
tion of said receiver.
9. A fault locating system for communication systems
13. A fault locating system for communication systems
comprising a station including a transmitter for trans
comprising a station including a transmitter for transmit-`
mitting a signal to a »distant receiver at a first frequency,
a receiver for receiving a signal from a distant transmitter
at a second frequency, an antenna, a duplexer coupling
said antenna to said transmitter and said receiver, said re
ceiver including a heterodyning means to convert the sig
nal at said second frequency to a signal having a given
intermediate frequency to provide an output signal from
said receiver when said receiver is operating, and »an os
cillator generating an output signal having a frequency
equal to the difference between said first and second fre
quencies coupled to said heterodyning means in the ab
sence of said output signal to simulate in conjunction with
ting a signal to a distant receiver at a first frequency, a
receiver for receiving a signal from a distant transmitter
at a second frequency, an antenna, a duplexer coupling
said antenna to said transmitter and said receiver, said re
ceiver including a heterodyning means to convert the sig
nal at said second frequency to a signal having a given
intermediate frequency to provide an output signal from
said receiver when said receiver is operating, an oscillator
generating an output signal having a frequency equal to
the diñerence between said first and second frequencies
40 associated with said heterodyning means and controllable
means to inject the output signal of said oscillatorinto
the leakage of signal of said lirst frequency through said
said heterodyning means in the absence of said output
Vduplexer into said heterodyning means a signal having
signal to simulate in conjunction with the leakage of sig
said intermediate frequency to determine the operating
-nal of said first frequency through said duplexer into said
condition of said receiver.
45 heterodyning means a signal having said intermediate
10. A fault locating system for communication systems
frequency to determine the operating condition of said
comprising a station including a transmitter for transmit
ting a signal to a distant receiver at a first frequency, a
14. A fault locating system for vcommunication systems
receiver.
’
_
receiver for receiving a signal from a distant transmitter
comprising a terminal station at each end of a communi
at a second frequency, an antenna, means coupling said 50 cation path; a plurality of repeater stations disposed inter
antenna to said transmitter and said receiver, said receiver
mediate said terminal stations; each of said repeater sta
including means to convert the signal at said second fre
tions including a first transmitter and a first receiver coop
quency to a signal having a predetermined frequency to
erating to provide communication by a first signal at a
provide an output signal from said receiver when said re
first frequency in a first direction on said communication
ceiver is operating, an oscillator generating an output 55 path, a second transmitter and a second receiver cooperat
signal having a given frequency associated with saidrcon
ing tol provide communication by a second signal at a
lverting means, and controllable means to inject the out
second frequency in `a second direction opposite to said
put signal of said oscillator into said converting means in
first direction on said communication path, a first and a
the absence of said output signal to simulate in conjunc
second antenna, a Ifirst means coupling said first antenna
tion with the leakage of signal of said first frequency 60 to said first receiver and said secondtransmitter, and a
through said antenna coupling means into said hetero
second means coupling said second antenna to said second
dyning means a signal having said predetermined frequen
receiver and said ñrst transmitter; onefof said terminal '
cy to determine the operating condition of said receiver.
stations including a third transmitter for transmitting said
1l. -rA fault locating system «for communication systems
comprising a station including a transmitter for transmit
ting a signal to a distant receiver at a first frequency, la
receiver for receiving a signal from a distant transmitter
at a second frequency, an antenna, means coupling said
first signal, a third receiver for receiving said second signal,
65 a third antenna, and a third means coupling said third
antenna to said third transmitter and said third receiver;
the other of said terminal stations including a fourth
transmitter for transmitting said second signal, a fourth
antenna to said transmitter and receiver, said receiver in
cluding -a heterodyning means to convert the signal at 70 receiver for receiving said first signal, a fourth antenna,
and a fourth means coupling said fourth antenna to said
said second frequency to a signal having a given intermedi
fourth transmitter and said fourth receiver; a heterodyning
ate frequency to provide an output signal from said re
means included in each of said receivers to convert the
ceiver when said receiver is operating, an oscillator gen
Isignal'received by its associated receiver to a signal hav
erating an output signal having a given frequency associ
ing
a given intermediate «frequency to provide anoutput
ated with said heterodyning means, and controllable means 75
3,045,113
ll
signal from said associated receiver when said associated
receiver is operating; an oscillator having an output sig
nal at a first given frequency associated with each of said
receivers of said first direction; an oscillator having an
output signal at a second given frequency associated with
each of said receivers of said second direction; control
means coupled to each of said oscillators; controllable
means to sequentially activate said control means of said
oscillators associated with said first and fourth receivers
to inject said oscillator output signal into said heterodyn
ing means included in said first and fourth receivers in
the absence of output signal from said fourth receiver,
said injected oscillator output signal in conjunction with
the leakage signal from said second and fourth transmit
ters passing through said first and fourth antenna coupling
means simulating at the output of said heterodyning
means of said first and fourth receivers a signal at said
intermediate frequency to sequentially determine the oper
ating conditions of said first and fourth receivers to localize
the failed equipment in said first direction; and controllable
means to sequentially activate said control means of said
oscillators associated with said second and third receiv
ers to inject said oscillator output signal into said hetero
dyning means included in said second and third receivers
in the absence of output signal from said third receiver,
12
leakage signal from said second and fourth transmitters
passing through said first -and fourth antenna couplingmeans simulating at the output of said heterodyning
means of said first and fourth receivers a signal at said
intermediate frequency to sequentially determine the op
erating conditions of said first and fourth receivers to lo
calize the failed equipment in said first direction; and
control-lable means to sequentially activate said control
means of said oscillators associated with said second
and third receivers to inject said oscillator output signal
into said heterodyning means included in said second
and third receivers in the absence of output signal from
said third receiver, said injected oscillator output signal
in conjunction with the leakage signal from said first and
third transmitters passing through said second and third
antenna coupling means simulating at the output of said
heterodyning means of said second and third receiver a
signal at said intermediate frequency to sequentially de
termine the operating conditions of said second and third
receivers to localize the failed equipment in said second
direction.
16. A fault locating system for communication sys
tems comprising a terminal station at each end of a com
munication path; a plurality of repeater stations disposed
intermediate said terminal stations; each of said repeater
stations including a first transmitter and a first receiver
said injected oscillator output signal in conjunction with
the leakage signal from said first and third transmitters
passing through said second and third antenna coupling
cooperating to provide communication by a first signal
means simulating at the output of said heterodyning
communication by a second signal
at a first frequency in a ñrst direction on said commu
nication path, a second transmitter and a second receiver
cooperating to provide
means of said second and third receiver a signal at said 30 at a second frequency
intermediate `frequency to sequentially determine the
said first direction on
operating conditions of said second and third receivers
and a second antenna,
in a second direction opposite to
said communication path, a first
a first duplexer coupling said first
to localize the failed equipment in said second direction.
antenna to said first receiver and said second transmitter,
l5. A fault locating system for communicaion systems
and a second duplexer coupling said second antenna to
comprising a terminal station at each end of a commu CO Cn said second receiver and said first transmitter; one of said
nication path; a plurality of repeater stations disposed in
termediate said terminal stations; each of said repeater
stations including a first transmitter and a first receiver
cooperating to provide communication by a first signal
at a first frequency in a first direction on said commu
nication path, a second transmitter and a second receiver
cooperating to provide communication by a second signal
terminal stations including a third transmitter for trans
mitting said first signal, a third receiver for receiving said
second signal, a third antenna, and a third duplexer cou«
40 pling said third antenna to said third transmitter and said
third receiver; the other of said terminal stations includ~
ing a fourth transmitter for transmitting said second sig~
nal, a fourth receiver for receiving said first signal, a
fourth antenna, and a fourth duplexer coupling said fourth
at a second frequency in a second direction opposite to
said first direction on said communication path, a first
antenna to said fourth transmitter and said fourth re
and a second antenna, a ñrst means coupling said first 45 ceiver; a heterodyning means included in each of said
antenna to said first receiver and said second transmitter,
receivers to convert the signal received by its associated
and a second means coupling said second antenna to
receiver to a signal having a given intermediate frequency
said second receiver and said first transmitter; one of said
to provide an output signal from said associated receiver
terminal stations including a third transmitter for trans
when said associated receiver is operating; an oscillator
mitting said first signal, a third receiver for receiving said 50 having an output signal at a frequency equal to the differ
second signal, a third antenna, and a third means coupling
ence of said first and second frequencies assoicated with
said third antenna to said third transmitter and said third
each of said receivers of said first direction; an oscilla
receiver; the other of said terminal stations including a
tor having an output signal at a frequency equal to the
fourth transmitter for transmitting said second signal, a
difference of said first and second frequencies associated
fourth receiver for receiving said first signal, a fourth 55 with each of said receivers of said second direction; a
antenna, and a fourth means coupling said fourth antenna
control means coupled to each of said oscillators; con
to said fourth transmitter and said fourth receiver; a
trollable means to sequentially activate said control means
heterodyning means included in each of said receivers
of said oscillators associated with said first and fourth
to convert the signal received by its associated receiver to
receivers to inject said oscillator output signal into said
a signal having a given intermediate frequency to provide 60 heterodyning means included in said first and fourth re
an output signal from said associated receiver when said
ceivers, said injected oscillator output signal in conjunc
associated receiver is operating; an oscillator having an
tion with the leakage signal from said second and fourth
output signal at a frequency equal to the difference of
transmitters passing through said first and `fourth duplexers
said first and second >frequencies associated with each of
simulating at the output of said heterodyning means of
said receivers of said first direction; an oscillator having 65 said first and fourth receivers a signal at said intermediate
an output signal at a frequency equal to the difference
frequency to sequentially determine the operating condi
of said first and second frequencies associated with each
tions of said first and fourth receivers to localize the
of said receivers of said second direction; a control means
failed equipment in said first direction; and controllable
coupled to each of said oscillators; controllable means
means to sequentially activate said control means of said
to sequentially activate said control means of said oscil 70 oscillators associated with said second aud third receivers
lators associated with said first and fourth receivers to
to inject said oscillator output signal into said heterodyn
inject said oscillator output signal into said heterodyning
ing means included in said second and third receivers in
means included in said first and fourth receivers in the
4the absence of output signal from said third receiver,
absence of output signal from said fourth receiver, said
said injected oscillator output signal in conjunction with
injected oscillator output signal in conjunction with the 75 the leakage signal from said first and third transmitters
3,045,11 a
13
14
passing through said second and third dupleXer-s simulat
dym'ng means to convert the frequency of the signal re-r
ceived from said transmitter to a signal having a given
intermediate frequency to provide an output signal from
ing at the output of said heterodyning means of said sec
ond and third receiver a signal at said intermediate fre
quency to sequentially determine theI operatin-g conditions
of said second and third receivers to localize lthe failed
equipment in 'said second direction.
'
17. A fault locating system for obtaining an indica
tion of the location of faulty equipment in a transmis
sion path including a transmitter and receiver disposed
said receiver when said receiver is operating, a source of
signals having a given frequency associated with said
heterodyning means, and controllable means to inject the
signal of said source of signals into said heterodyning
means in the absence of said output signal to simulate at
the output of said heterodyning means a‘signal having
in said path, said receiver including means to convert the 10 said intermediate frequency to, determine the operating
condition of said receiver whereby the presence of output
frequency of the signal received from said transmitter to
signal from said receiver gives an indication that said
a signal having a predetermined frequency to provide an
transmitter includes the faulty equipment and the, absence
output signal from said receiver when said receiver is
of‘output signal from said receiver gives an indication
operating and a source of signals having a given fre
quency coupled to said converting means inthe absence 15 that said receiver includes the faulty equipment.
20. A fault locating system for obtaining an indica- of said output signal to simulate at the output of said
tion of the location of faulty equipment in a transmission
converting means a signal having said predetermined fre
path including a plurality of transmitters and 'receivers
quency to determine the operating condition of said re
alternately arranged in tandem to provide communica
ceiver whereby the presence of output signal from said
receiver gives an indication that said transmitter includes 2o, tion in said path by a signal at a predetermined frequency, Y
each of said receivers including a heterodyning means to
the faulty equipment and the absence of output signal
from said receiver gives an indication that said receiver
convert the signal at said predetermined frequency to a
includes the faulty equipment.
signal having a given intermediate frequency to provide
an output signal yfrom its associated one of said receivers
18. A fault locating system for obtaining an indica
tion of the location of faulty equipment in a transmission 25 when said ,associated receiver is operating, a source of
signals having a lgiven frequency associated with each of
path including a transmitter and receiver disposed in said
said heterodyning means, and controllable means to se
path, saidlreceiver including a heterodyning means to
convert the frequency of the signal received from said
quentially inject the signals of said source of signals into
said heterodyning means of said associated receiver in the
transmitter to a signal having a given intermediate fre
quency to provide an output signal from said receiver 30 absence of output signal from the terminal one of said
receivers to simulate at the output of said heterodyning
when said receiver is operating and a source of signals
means a signal having said intermediate frequency to se
having a given frequency coupled to said heterodyning
quentially determine the operating condition of said re
means in the absence of said output signal to simulateat
ceivers preceding from said terminal receiver to the ter
the output of said heterodyning means a signal having
said intermediate frequency to determine the operating 35 minal one of said transmitters whereby the presence of
output signal from said terminal receiver gives an indi
condition of said lreceiver whereby the presence of output
cation that equipment succeeding said associated receiver
signal from said receiver gives an indication that said
is faulty and the absence of output signal from said ter
minal receiver gives an indication that said associated
of output signal from said receiver gives an indication
40 receiver includes faulty equipment.
that said receiver includes the faulty equipment.
19. A fault locating system for obtaining an indication
References Cited in the file of this patent
of the location of faulty equipment in a transmission
UNITED STATES PATENTS
path including a transmitter and receiver disposed in said
path, said receiver including a transmitter and receiver
Thompson ____________ __ Oct. 5, 1954
2,691,065
disposed in said path, said receiver including a hetero
Schultz ______________ __ Dec. 15, 1958
2,864,943 v
transmitter includes the faulty equipment and the absence
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