вход по аккаунту


Патент USA US2406034

код для вставки
Aug. 2E, E94. ‘
4 Filed Aug. 24, 1943
4 Sheets-Sheet l
__ „El“.
Àug- 20, 1946»
w. A. PHELPs
Filed Aug. 24, 1943
J4 Sheets-Sheet 2
dnâ ë 4.
Àug. 20, 1946.
W. A. PHELPS ' '
Filed Aug. 24, 1945
4 Sheets-Sheet 3
A from/Ey
., m, m4.
W. A.
s v.. s T E M
Filed Aug. 24, 1945
4 Sheets-¿Sheet ¿l
F76 4
-- DE
nrs. ,
Patented Ang. 20, i946
Walter A. Phelps, Madison, N. J., assignor to Bell
Telephone Laboratories, Incorporated, New
York, N. Y., a corporation of New York
Application August 24, 1943, Serial N0. 499,773
5 claims. ’(01.179-4)
The invention relates to carrier wave signaling
systems and particularly to carrier telegraph sys
The invention is particularly applicable to, al
quency carrier telegraph system employing fre
quency modulation, operated over a high fre
quency channel employing unsynchronized high
frequency carrier sources associated with the
group modulation and demodulation apparatus at
as a link therein, a multichannel voice-frequency
its opposite terminals.
carrier telegraph system utilizing in each channel
These objects are attained in accordance with
two tones of voice frequency slightly separated in
the invention by sending out over the high fre
the frequency spectrum, respectively for the
quencyV line of such a system, along with the tele
transmitted “marking” and “spacing” telegraph
graph signal-modulated carriers, an unmodulated
signal impulses representing a telegraph message,
pilot wave of suitable frequency, which at the re
which are separately detected at the receiving
Áceiving‘end of the system is combined in a modu
end of the system and applied to the opposing
lator with the received signal-modulated carriers
windings of the channel polar receiving relay
prior to their separation and detection, to trans
causing its operation to repeat the marking and 15 form them to desired 10W frequencies. The final
spacing signals. Where it is desired to transmit
modulation process effectively cancels out from
the voice-frequency telegraph signals of such sys
the received signals any variations introduced by
tems between widely separated points efñciently
deviations between the frequencies of the unsyn
and cheaply, one of the voice-frequency carrier
chronized high frequency carrier sources asso
telegraph terminals >may be located at each of 20 ciated with the group modulator and demodulator
those points, and a portion of an existing high
in the high frequency link.
frequency transmission system extending between
'I'he various features and objects of the inven
those points, for example, a high frequency chan
tion will be better understood from the following
nel of a single side-band (suppressed carrier)
detailed description when read in conjunction
telephone system, utilized for transmitting the 25 with the accompanying drawings in which:
telegraph signals between the voice-frequency ter
Figs. 1 to 3 in combination show schematically
though not limited to, such a system including
minals. In that case, a group modulator with an
a two-Way carrier telegraph system employing
associated high frequency carrier source at the
frequency modulation, embodying the invention;
transmitting end of the high frequency channel
would be utilized for stepping up the fundamental 30 Figs. 4 to 7 show curves used to explain the in
voice-frequency carrier channels to the higher
frequencies required for transmission over it, and
Figs. 1 to 3, when placed side by side in that
a group demodulator with an associated high fre
order with Fig. 1 at the left, show a complete two
quency carrier source at the receiving end of the
way carrier telegraph system providing four mes
high frequency channel, for stepping down the 35 sage channels in each direction, consisting of a
received carrier telegraph channels to voice fre
west and an east two-Way voice frequency carrier
quencies for reception.
telegraph termina1 and an intermediate two-way
In certain of the existing high frequency sys
high frequency transmission link HFL, which may
tems which may be used in such a combination
be one two-Way high frequency channel of a
system, the high frequency oscillators associated 40 multichannel single side-band carrier telephone
with the group modulator and demodulator in
system, converted to telegraph use.
the high frequency channel for each direction are
The high frequency transmission link HFL of
normally operated unsynchronized. They may,
the combination system, as shown in Fig. 1, com
therefore, have instantaneous frequency differ
prises a west-to-east one-way high frequency re
ences between them at times which may be suffi
cient, particularly where the telegraph signals are
applied to the voice-frequency carriers by fre
quencyv modulation, to introduce intolerable sig
nal bias variations in the received telegraph
45 peating path EA and an east-to-west one-way
high frequency repeating path WA coupled at
their west and east terminals in conjugate rela
tion with each other and in energy transmitting
relation with the west two-way line section LW
50 and the east two-way line section LE by means
AAn object of the invention is to reduce signal
of the hybrid repeating coil HCW and the asso
distortion in carrier telegraph systems.
cited line balancing network Nw, and the hybrid
A more specific object is to reduce to an unob
repeating coil HCE and associated line balancing
jectionable amount signal bias variations in the
network NE, respectively. The path EA includes
telegraph channels of a multichannel voice-fre 55 in its input and output the band-pass filters F23
and F24 respectively adapted to pass only a band
of frequencies corresponding to the total fre
quency range of the modulated voice-frequency
carriers and pilot wave generated at the West
voice-frequency carrier telegraph terminal, and
the path WA in its input and output the band
contacts under control of the telegraph keys K2
to K4 in the associated subscriber’s loops, to pro
vide frequency-modulated voice-frequency car- '
rier Waves representing respectively different
telegraph messages to be transmitted. The fre
quency-modulated carriers in the output of oscil
lators O1 to O4 in the four channels I to 4 pass
respectively through the associated sending band
filters F1 to F4, respectively adapted to pass the
pass filters F25 and F26 respectively adapted to
pass only a band `of frequencies corresponding to
the total frequency range of the modulated voice
frequency bands 1445i35 cycles, 1615x135 cycles,
frequency carriers and pilot wave generated at
1785i35 cycles and 1955i35 cycles.
the east voice frequency carrier telegraph termi'-`
Irl addition to the four carrier oscillators O1
nal in the manner to be described. The path EA
to O4 at the West terminal, there is provided a
also includes in its input, to the east of filter F23,
Vfifth oscillator O5 which generates another voice
a group modulator M1 and associated carrier
source O11 generating the high frequency f1, and 15 frequency of 2380 cycles which passes unmodu
lated through the associated filter F5 selective to
in its output, to the West of band-pass filter F24, a
its frequency. The outputs of the ñve filters F1
group demodulator D1 with an associated carrier
to F5 are bridge in parallel across the common
source O12 of corresponding nominal high fre
two-Way line section LW so that the four fre
quency f1. The path WA also includes in its in
put, to the West of filter F25, a group modulator 20 quency-modulated carriers and the unmodulated
pilot Wave of a frequency of 2380 cycles are super
M2, with an associated carrier source O12 of the
posed in that line section and pass thereover to
high frequency f2; and in its output to the east
the West terminal of the high frequency trans
of ñlter F25 a group demcdulator D2 with an asso~
mission link HFL.
ciated carrier source O14 of the nominal high fre
Similarly, at the east end of the system the
quency f2.
25 transmitting
circuits of the east voice-frequencyA
The transmitting circuits of the two-way voice
carrier telegraph terminal, as shown in Fig. 2,
frequency carrier telegraph terminal at the west '
include four oscillators Os to O9 normally gen
and of the combined system, as shown in Fig, 1,
erating carrier currents of the different voice
include four oscillators O1 to O4 normally gen
erating carrier currents of the voice frequencies
frequencies 595, ‘765, 935, 1105 cycles for the four
1445, 16115, 1785 and 1955 cycles for the four
transmitting channels I to 4. These oscillators
carrier telegraph channels in the east-to-West
direction. The oscillators O1 to Os are adapted
to be respectively controlled by the associated
may be» of the vacuum tube type illustrated for
sending circuit comprising sending relay SRs and
the oscillator O1 in channel I which is shown in
more detail. Thesecarrier currents are respec 35 the associated subscriber’s key Ks, the sending
sociated with the respective oscillators, to impress
telegraph signals constituting a separate message
relay SR1 and the associated subscriber’s key K7,
the sending relay SRs and the associated sub
scriber’s key Ks, or the sending relay SR@ and
on each carrier.
the associated subscriber’s key K9 in a manner
tively modulated by separate sending circuits as
The sending circuit in chan
nel I comprises the polar telegraphv sending relay 40 similar to that described for the similar channels
at the west terminal of the system, to swing thev
SR1 which is controlled by the telegraph key K1
or Vits equivalent in one subscriber’s loop. Sim
ilarly,> the sending circuit in each of the other
three channels comprises one of the polar tele
graph sending relays SR2 to SR1 respectively
controlled by one of the operating keys K2 to K4,
or theV equivalent, in other respective subscribers’
carrier for each channel 35 cycles to one side of
its normal frequency value for a marking signal
and 35 cycles to the other side for a spacing
signal. In addition to the four carrier oscilla
tors O5 to Os at the east terminal, there is a fifth
carrier oscillator O10 generating' a frequency of
2550 cycles which is unmodulated by telegraph
signals.. The marking and spacing telegraph
When the key K1 in channel I is closed to
provide an energizing circuit from the associated 60 signal outputs of the carrier oscillators Os t0 On
and the unmodulated output of the 2550-cycle
Y battery to the operating Winding of sending. relay
oscillator 01o are respectively selected by the
SR1, that relay is operated to its marking con
transmitting band filters Fe to F111 and are super
tact m1, and when the key K1 isì opened to de
posed in the two-Way line section LE over which
energize the operating Winding, that relay is
operated toits spacing contact s. The relay con 55 they pass to the east terminal of the high fre
quency transmission line HFL.
nectionsto oscillator O1 are such that the ca
The voice-frequency carrier telegraph receiv
pacitance in the tuned circuit of that oscillator
ing circuits at the east terminal of the system,
is changed >by a suñìcient amount for the two
shown in Figs. 2 and 3, include a balanced mod
operating conditions of relay SR1k to swing the
carrier generated by the oscillator 35 cycles to 60 ulator M31 which may be of the second order
type, such as disclosed, for example, in F.Y A.
one side of the Vnormal carrier frequency (1445
Cowan Patentk 1,959,459. The modulator M2 in
cycles) for a marking signal and 35 cycles on
cludes four copper-oxide rectifier units connected
thepother side of the normal carrier frequency
for a spacing signal. Thus, by alternately clos
ing and Opening the‘key K1, the carrier Wave of
nominal frequencyy 1445 cycles in channel I may
be frequency modulated in accordance with a
telegraph message to be transmitted.
_ Similarly, the; frequencies of the carriersV gen
erated, by the similar oscillators O2 to O4, indi
’ cated by boxes, in` channels 2 to 4, respectively,
may be. shifted i235 cycles from the nominal
values of 1615, 1785 and 1955 cycles, respectively,
by operation of the, associated sending relay SR2
to VSlis` alternatelyv to their marking andv spacing
in- a Wheatstone bridge formation; an output
: transformer I connected across one diagonal of
the bridge, one input circuit, including the band
pass filter F11, passing the frequency range 1375
2025 cycles corresponding to the frequency range
occupied by both the marking andY spacing sig
nals of all four voice-frequency carrier telegraph
channels. generated at the west terminal, con
nected by transformer 2 across that same- diagonal of the bridge, andï a- second» input circuit,
including the narrow bandÍ filter F12 selective to
the frequency 2380 cycles» produced by the pilot
wave oscillator O5 at the west terminal, con
nected by transformer 3 across the other “con
jugate” diagonal of the bridge. The two input
inator D1v11 and the spacing discriminator Der
having their inputs connected in parallel to the
output of the current limiter CL1', a current of
constant amplitude and of a frequency whichv
through transformer 4 from the two-way line 5 may be steady or variable, depending on whether
section LE terminating the east end of the high
the channel is standing idle or transmitting sig
frequency channel HFL with the waves of voice
frequency received from that channel, the pass
The discriminators DM1 and Ds1 consist merely;
frequency ranges of filters F11 and F12 being
of high- and low-pass ñlters or tuned circuits,
such as to prevent the outgoing signal outputs 10 respectively, of simple design. Their character
of the transmitting band filters Fs to F1o bridged
istics are shown in Fig. 5 with that of the re
across the line section- LE from feeding into the
celving channel band filter F13, drawn in dotted
input of «the modulator M3.
lines to show the band limits. When the re
Neglecting for the" momentl theÁ effect of any
ceived carrier current is at the marking fre
circuits of modulator M3 are fed in common
variations produced in the transmitted signal 15 quency fm, the loss through the marking dis
bearing voice frequency carriers because' of var
criminator Divn is low and the loss through the
iations between the frequencies of fthe unsyn
spacing discriminator Dsl is high. Therefore, the
chronized high frequency carrier oscillators in
marking current out of the discriminator DM1 is
the intermediate high frequency carrier link
at a maximum and the spacing current out of
HFL, the operation of the voice frequency car 20 the spacing discriminator Ds1 is at a minimum.
rier telegraph receiving circuits at the east ter
As lthe frequency is shifted from fm to fs, the loss
minal is as follows: The four frequency-modu
through the discriminator DM1 increases and that
lated carrier waves of the frequencies 14451-35
through the discriminator Ds1 decreases. When
cycles, 16151-35 cycles, 1785i3‘5 cycles and
the carrier reaches fs, the current out of the dis
1955i35 cycles and the one unmodulated pilot 25 criminator DS1 has reached a maximum and that
wave of 2380 cycles received in the line section
LE over the high frequency carrier link I-IFL
from the west terminal of the system will pass
out of the discriminator DM1 has reached a min
imum. It will be noted that the modulation
process in Ms has turned over the frequency de
through the transformer 4 to the conjugate input
viation. The marking frequency in channel l
circuits of modulator M3. The four signal bear 30 started out from the west terminal as 1955-35
ing waves will be selected by fthe band filter F11
cycles and became 4254-35 cycles in the output
and will be impressed by transformer Z on one
of modulator M3.
diagonal of the copper-‘oxide rectifier bridge of
The currents out of the discriminators DM1 and
the modulator M3 and will combine with the
Ds1 are ampliiied and rectified in the marking
2380-cycle unmodulated pilot wave, selected by 35 detector MD1 and the spacing detector SD1, re
ñlter F12 and impressed by transformer 3 on
spectively, and the result is a push-pull current
the other conjugate diagonal of the bridge, to
in the marking and spacing windings of the
produce the desired output frequencies shown
polar receiving relay RR1, respectively connected
in Table 1 to the right of modulator M3. These
to the outputs of those detectors. Typical mark
desired frequencies are respectively selected and 40 ing and spacing winding currents in the receiv
passed on by the narrow receiving channel band
ing relay RR1 are shown in the curves of Fig. 6.
filters F13, F14, F15 and F16 connected in parallel
The push-pull currents in the lwindings of the
to the output of modulator M3, the undesired
relay RR1, produced by the detected marking
products of modulation in modulator M3 being
and spacing current-s, cause the armature of that
rejected by those filters. From this point it will
relay to move back and forth between its mark
be suiîlcient to trace the path in one channel only
ing contact m and its spacing contact s, which
as all perform in a similar manner.
repeats the telegraph signals to the subscriber’s
Considering receiving channel I, the current
receiving loop connected to those contacts caus
out of the 425-cycle iilter F1a swings back and
ing the operation of the printer, sounder or other
forth between 4254-35 cycles and 425-35 cycles
receiving or recording device in that loop in
for the received marking and spacing signals.
accordance with the repeated signals. In re
This current of varying frequency then passes
ceiving channels 2, 3 and 4, the receiving appa
into the current limiter CL1 comprising the two
ratus is similar to the receiving apparatus in
transformer coupled-amplifying vacuum tube
channel I , as indicated by the use of the same
stages 1 and 8, a portion of the output of the
identification characters but with suitable sub
second stage tube 8 being picked olf through a
scripts corresponding to the number of the chan
third winding 9 on output transformer l0, recti
nel, and operates in response to the marking and
iied by the full-wave rectifier Il and passed
spacing signals in the output of modulator M3
through the series resistance l2 in the control
of the frequencies 595i35 cycles, 765i35 cycles
grid-cathode circuit of tube 8 to provide a vary 60 and 935i35 cycles, respectively, in a manner
ing direct current bias on its control grid. The
similar to that which has just been described for
circuit constants of the current limiter CL1 and
channel I to cause operation of the channel re
those of the similar current limiters in the other
ceiving relays RRZ to RR4 to repeat these signals
receiving channels at both terminals of the sys
to the subscriber’s receiving loops respectively
tem are selected such as to produce a current 65 connected to the channels.
input-current output characteristic resembling
Similarly, the voice-frequency telegraph re
that of Fig. 4. It will be observed that for a
ceiving circuits at the west terminal of the sys
wide range of input levels, the output is nearly
tem, as shown in Fig. 1, include a balanced second
constant. The purpose of this limiter circuit is
order modulator M4 of the copper-oxide recti
to provide at its `output current of closely con 70 fier bridge type, similar to the modulator M3 at
stant amplitude, regardless of the frequency
the east terminal, having its conjugate input
variation of its current input and regardless of
branches respectively including a band-pass filter
the rather wide swings in amplitude which may
F17 and the narrow band-pass filter F1a fed in
be >caused by line equivalent variations. There
common through transformer 5 from the two
then will be impressed on the marking discrim 75 way line section LW terminating the west end
of the high >frequency transmission link I-IFL,
and its' single output circuitcoupled .by output
transformer E .in .parallelto the inputsof the'four
telegraph 'terminal to the voice frequency tele
graph receiving apparatus at the east terminal,
and vice versa, the action of the high frequency
receiving band filters F19 to F22 in the receiving
carrier telegraph channels l to Il. 'The four fre
quency-modulated carrier Waves of the frequen
cies 595135 cycles, 765i35 cycles, 9351-.35 cycles
and 1105135 cycles generated by the sending
circuits at the east terminal and the accompany
ing unmodulated pilot Wave of the frequency 2550
cycles >generated at that terminal pass from the
two-Way line section LW through the input trans
former f5 to the modulator Mi. The four signal
apparatus in the intermediate high frequency
transmission link HFL, not previously described
quency variation and regardless of the .wide
swings in_amplitude in the current input caused
by line equivalent variations. The output of the
the same pass range as the iilter F23, and are
in detail, is as follows.
The easterly directed voice-frequency carrier
channels and the accompanying unmodulated
pilot wave generated by the voice-frequency car
rier >telegraph transmitting apparatus at the
west terminal passing into the two-Way line sec
tions LW at that terminal, will be impressed by
the hybrid coil HCW on the input of the West-to
east repeating path EA in the link I-lFL in which
bearing waves are selected out 'by the band filter
F11 passing the frequency range 525 to 11'75 cycles 15 they will be selected by the band-pass filter F23
having a pass range which includes all of those
in one input branch, and are combined in the
frequencies but excludes those of the westerly
modulator 'M4 with the 2550-cyclerpilot current
directed voice-frequency channels and pilot Wave.
selected >by the ñlter Fig in the other conjugate
The selected voice frequency-modulated carrier
input branch, to produce the four desired output
frequencies in the output of the modulator, shown 20 output of the filter F23 in the path EA will he
impressed on the modulator M1 in Which it Will
in Table 2 to the left of that modulator. These
be combined with the high frequency carrier of
desiredfrequencies pass through output trans
nominal value f1 supplied from the associated
former 6 and are respectively‘selected by the
oscillator O11, to step up the voice-frequency
receiving band filters F19 to F22 in the four receiv
ing channels, the undesired products of modula 25 carrier channels and the pilot Wave, to frequen
cies suitable for transmission over that path. At
tion -in the output of the modulator M4 'being
the east terminal 0f the high frequency path EA,
rejected by these ñlters.
the received carrier channels of stepped-up fre
In receiving channel I at the West terminal,
quencies are combined in the demodulator D1
the current output of filter F19 swings back and
forth between 1445-i-35 and 1445-35 cycles with 30 with a high frequency carrier Wave of the same
nominal frequency f1 supplied to the demodulator
the marking and spacing signals. This >current
from the associated oscillator O12, to step the
of varying frequency then passes through the
carrier channels down again >to their original
individual current limiter CL5 for channel l,
frequencies Which are selected by the band-pass
which provides an output current of substan
tially constant amplitude regardless of the fre 35 filter F24 in the output of the path EA, having
impressed by the hybrid coil HCE on the two
Way line section LE. The received voice-fre
quency channels and pilot Wave will pass from
current limiter CLs is impressed on the parallel
connected inputs of the marking and spacing 40 the line section LE to the voice-frequency carrier
telegraph receiving circuits of the east terminal
discriminators Divis and Us5, similar to the cor
described above.
responding discriminators in each receiving
Similarly, the Westerly directed voice-frequency
channel at the east terminal just described and
carrier channels and the unmodulated pilot Wave
operating in similar manner. The currents out
of the discriminators D215 and Dss are respec
tively amplified and detected in the marking
detector MD5 and the spacing detector SDs, and
the resulting detected currents are applied in
push-pull to the marking and spacing windings
of- the polar receiving relay RRs to cause alter
nate operation of its armature to its marking and
spacing contacts to repeat the telegraph signals
to the subscriber’s receiving loop associated with
that channel.
. generated in the voice-frequency carrier tele
graph transmitting apparatus at the east termi
nal of the system of Fig. l, passing into the tivo
way line section LE will be impressed by the hy
brid coil HCE on the east-to-West repeating path
WA of the intermediate high frequency link HEL
and will be selected by the band-pass filter F25
having a suitable frequency pass range. The se
lected frequencies in the output of the ñlter F25
will be combined in modulator M2 in the input of
Similarly, the frequency-modulated carrier 55 the path WA with the high frequency carrier of
nominal frequency fz supplied from theiassoci
outputs of the filters F20 to F22 in the telegraph
ated carrie;` oscillator O13, to step-up all of the
receiving -channels 2 to A at the West terminal,
voice-frequency channels and the pilot wave to
of the frequencies ,1615x351 cycles, 1785i35
high frequencies suitable for transmission over
cycles and 1955i35 cycles, are respectively oper
ated -on by the current limiter, marking and spac 60 that path, and at the west terminal of the high
frequency link HFL the received Waves Will be
ing discriminators, and the marking and spacing
combined in the demodulator D2 with the high
detectors of the corresponding channels in a
frequency carrier of nominal frequency f2 sup
manner similar to that which has been described
plied from the associated carrier oscillator 012
for the similar elements in channel l, to provide
to step them down again to their original voice
respective alternate operation of the channel
frequencies. These frequencies Will be selected
receiving relays RRG to RRS to their marking
by the band-pass filter F25 of suitable transmis
and spacing contacts, to repeat the marking and
sion frequency range, and impressed by the hy
spacing telegraph signals for those channels to
brid coil HCW >on the `two-way line section LW
the connected subscriber’s receiving loop to oper
ate a printer, sounder or other receiving or re 70 from which they will pass to the voice-frequency
carrier telegraph receiving circuits of the west
cording device.
terminal Adescribed above.
In the above description of the passage of the
Unless the -high frequency -carrier Sources as
frequency-modulated carrier waves and of the
sociated with 'the group modulator and the group
unmodulated pilot wave from the transmitting
apparatus at the West voice frequencyl carrier 75 demodulator the vrepeating path fOr @30h -di
',rection in `thehigh frequency link HFL are def
initely synchronized over the line, their frequen
cies are never exactly alike, and in the particular
high frequency channel with which the voice
frequency carrier telegraph channels of the in
vention were actually combined, it was foundv
that they may differ at times by as much as 15
carrier communication channels >and a separate ’
pilot channel, means at a transmitting point for
combining each of said channels with a high fre
quency carrier for transmission, means ata re
ceiving point for combining the received high
frequency waves with a carrier of nominally the
same high frequency as the high frequency car
cycles. It has been found by experiment that
rier at the transmitting point, to demodulate the
such a 15-cycle deviation between the high fre'
quency carrier oscillators with a frequency-mod 10 received communication channels and the re
ceived pilot channel, and modulating means for
ulation voice frequency carrier telegraph system
combining each of the demodulated carrier chan
such as illustrated in Figs. 1 to 3, but not -in
nels with the demodulated pilot channel to com
cluding the arrangements of the present inven
pensate for any frequency differences between
tion, would result in a signal bias variation of
about 20 per cent in the telegraph receiving chan 15 the high frequency carriers at the transmittingl
and receiving points tending to distort the trans
nels. The characteristics from which this was
mitted carrier communication channels.
deduced is shown in Fig. 7. 'I‘he curve of that fig
2. In combination in a carrier signaling sys-l
ure shows the percentage signal bias variation
tem, a high frequency transmission line, a plu
produced in a telegraph receiving channel of
the 'system for different values of frequency de 20 rality of sources respectively generating carrier
waves of different low frequencies, another source
viation in cycles between the high frequency car
generating a pilot wave of predetermined ‘fre
rier oscillators associated with the group mod
quency, means to modulate each of said carrier
ulator and the group demodulator at the input
waves with a diiferentmessage, means to im
and output, respectively, of the high frequency
channel feeding it.
Let us assume that oscillator O11 associated
with the group modulator M1 in the west-to-east
side of the high frequency link HFL in the sys
press the modulated carrier waves and the un
25 modulated pilot wave on the input o'f said line,
a group modulator with an associated high fre
quency carrier source in the input of said line
for stepping up the frequencies of all of the im
pressed waves to those suitable for transmission
tem of Fig. 1, is at the correctfrequency, and
that the oscillator O12 associated with the de 30
over that line, a group demodulator withr an
modulator D1 in the output of that side is l5
associated high frequency carrier source of the
cycles lower. The easterly directed channel 4
same nominal frequency as the first high fre
current at frequency 1445i35 cycles, after pass
quency carrier source, in the output of said line
ing through the demodulator D1 at the east ter
minal of the high frequency channel would, in a 35 for stepping down the received waves to their
conventional frequency modulation system, have
original frequency values, a second modulator
fed from the output of said line, for combining
each of the applied low frequency-modulated
sumed condition of oscillator O12 being 15 cycles
carriers with the received unmodulated pilot wave
low. By the time this signal reached the receiv
ing relay RRi in receiving channel I at the east 40 to transform the former to desired lower fre
quencies, and to eliminate therefrom any varia
terminal, it will have a light bias of about 20
tions therein caused by any frequency differences
per cent, as indicated by the curve of Fig. '7, above
between the high frequency carrier sources as
the point -15 on the frequency axis. But in the
sociated with the group modulator and group de
circuit illustrated in Figs. 1 to 3, a pilot wave of
the frequency 2380 cycles has been transmitted 45 modulator of the high frequency line, and means
to separate the resulting modulated carrier waves
along with the channel frequencies and this also
and to separately detect the message components
emerges from the output of the demodulator Di
15 cycles low. When these two currents are com
3. In a carrier wave signalingsystem including
bined in the modulator M3 in the common re
frequency carrier signal transmitting and
ceiving circuit at the east terminal of the sys 50
receiving circuits at each terminal thereof and
tem, a combination of this type ensues:
a frequency of 1445i35~15 cycles under the as
an intermediate two-way high frequency trans
mission link including group modulating and de
modulating devices with associated high fre
935i35 cycles (l)
quency carrier sources for respectively stepping
which is the same frequency as would be obtained 55 up the low frequency carrier signals received by
when the frequencies from the oscillators O11
said link from the low frequency carrier signal
and O12 were considered to be exactly the same.
transmitting circuits at each terminal to high
Thus, the frequency variations introduced in the
frequencies suitable for transmission over that
intermediate high frequency line have been ef
link, and for stepping down the high frequency
fectively cancelled out in the final modulation 60 carrier signals received at each terminal over
process. The same would be truein the case of
said link to their original frequency values be
each of the other channels. Thus the scheme
fore supplying them to the low frequency carrier
of the invention may be used to make the received
signal receiving circuits at that terminal, the low
frequency in any frequency-modulated carrier
frequency carrier signal receiving circuits at each
telegraph channel independent of any frequency 65 terminal including other modulating means for
variation between separate and unsynchronized
combining each of the received low frequency
(2380-15)-[(1445-15);35 cyclesl:
carrier oscillators associated with the modu
lator and demodulator in any intermediate high
carrier signals with a carrier Wave of suitable
frequency to transform the former to desired low
frequency values before they are separated and
Various modifications of the circuits illustrat 70 the signal components detected therefrom, and
frequency carrier link.
ed and described which are within the spirit and
scope of the invention will occur to persons skilled
in the art.
What is claimed is:
means to reduce distortion of the detected sig
nal components due to relativeinstantaneous fre
quency differences between the high frequency
carrier sources in the intermediate high frequency
1. In combination, a group of low frequency 75 transmission link comprising means for supplying
said carrier waves of said suitable frequency comf- i
bined with each receivedlow frequency 'carrier
signalsin the low frequency carrier signal"A re
c'eíving circuit at each terminal, over said high
frequency transmission link from the other ter
minalso that they are subjected to the same
frequency variations in that link as the trans
mitted carrier signals.
»4. In combination in a multiplex carrier tele
graph system, means for producing a plurality
of different voice frequency carriers respectively
frequency modulated with a different telegraph
message, a high frequency transmission line sup
plied With said modulated carriers and including
in its input modulating means with an associated
high frequency carrier source, for stepping up the
supplied Waves as a group to the high frequencies
suitable for transmission thereover, and in its
output demodulating means with an associated
high frequency carrier source for stepping down 20
theV Waves received over the line as a group to
carriers in said‘other modulating means, -over
said high frequency line so that it is subjected
to the same frequency variations as the modu
lated carriers transmitted thereover.
5. The combination of claim 4 in Which each
of said plurality of different4 voice-frequency
carriers frequency modulated with a different
message is obtained «by changing the tuning of
a different Voice-frequency carrier oscillator
under control of associated keying means so that
the generated carrier is swung a given number
of cycles to one side of the normal carrier fre
quency to produce a marking signal andl the
same amount to the other side of the normal
carrier frequency to produce a spacing signal,
the receiving circuit of said system comprising
separate nlters for respectively `selectingboth the
marking signal component and the spacing signal
component in each modulated carrier VWave in
the output of said other modulation means at
the receiving terminal, separate current Alimiters
their original frequencies, another modulating
means for combining the modulated carriers of
for respectively producing from the current out
put of each of said filters a current of substan
the former to suitable frequency values, means
means for separating the marking and spacing
signal impulses in the resulting Wave, detectors
tially constant amplitude, regardless of frequency
low' frequencies received over said- line with a
carrier Wave of suitable frequency to transform 25 and amplitude variations therein, other ñltering
for separating lthe resulting modulated carriers
and separately detecting the telegraph »message
for separately detecting said marking and spacing
signal impulses and a receiving telegraph relay
components therefrom, and means to reduce dis
tortion in the detected message components re 30 having opposing windings to which the detected
marking and spacing impulses are respectively
sulting from >fo'rtuitous frequency differences be
applied to cause the operation of said relay to
tween the high frequency carrier sources associ
repeat the marking and spacing signals of the
ated with the group modulating and demodu
lating means in said high frequency line, com
prìsíng means for Supplying said carrier Wave of 35
suitable frequency combined with the modulated
Без категории
Размер файла
1 180 Кб
Пожаловаться на содержимое документа