Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ wo 95/34167 2 ~ 9 2 3 4 1 P~
METHOD AND APPARATIJS FOR ISN~.:UL/lN~:;, TRaN~ LlN~,
STORING AND DECODING OF DATA
BACKGROUND OF THE INVENTION
2
3 The present invention relates to the
4 tr;3nr-;rs;on of information over a communication
5 link, such as a telephone line, and to the encoding
6 and ~l.ocorl;n~ of data and to the storage of such
7 encoded information. This application is a
8 cnnt;nll~tion in part of U.S. patent application No.
9 08/254,164, filed June 6, 1934 for PROCESS AND
10 APPARATUS FOR TRANSMITTING VIDEO SIGNALS OVER A
11 COMMUNICATION LINK.
12 Common or ordinary voice grade telephone lines
13 have been utilized for a number of years in
14 connection with the tr~nrm; ~r; on and reception of
15 signals, other than audio signals. Common or
16 ordinary voice grade telephone lines are telephone
17 lines that have subst~nt i~l l y the same predetermined
18 or standard bandwidth, i.e. about 0-3600 Hz, that
19 make up the substantial maj ority of telephone lines
20 in the Unitea States, as well as in foreign
21 countries, for providing the telephone linkage among :
22 residences, public tPl Prhnnf~r and most businesses.
23 Ordinary telephone lines have also been used to
24 transmit video signals. The ordinary telephone ~ :
2~ line, having a bandwidth of about 0-3600 Hz or a
26 transmission rate of about 9 . 6 kbaud, does not
27 transmit, in real time, a typical full motion
28 commercial television type black and white and/or _ :~
29 color video image. The commercial television system
displays ~12 X 512 pixel images at 30 frames per
31 second and uses about 6 MHz bandwidth while
32 simultaneously transmitting video and audio signals.
Wo 95134167 I~,IIUV ~
21 9234l
Because of =the large bandwidth required, prior art
2 systems do: not enable one to transmit ~ull motion
3 images over an ordinary voice grade telephone line.
4 In connection with the transmission of video and
5 audio signals, the video signal is transmitted over
6 the ordinary telephone line using a first,
7 predetermined bandwidth of the limited bandwidth of
8 the ordinary telephone line and the audio signal is
9 transmitted using a second, pr~rlPt.~rm; n,orl bandwidth
10 of the limited bandwidth of the ordinary telephone
11 line. U.S. Patent ~o. 4,849,811 to Kleinerman,
12 issued July 18, 1989, and entitled "Simultaneous
13 Audio and ~ideo Transmission with Restricted
14 Bandwidth" describes a system in which modulated
digitized image signals and ~iltered voice signals
16 are transmltted together over an ordinary t~ ph~n
17 line whereby still or :Ereeze-frame images are
18 provided with ~ r;~nying video. The digitized
19 image signa=ls are in the range of 2400 to less than
about 400 Hz. A low pass filter limits the voice
21 signals to ~a range outside the digitized image
22 signals so that the image signals and voice signals
23 can be transmitted at the same time but over
24 separated sections of the limited bandwidth o~ the
telephone line. Because o~ the separate barLdwidths
26 used, means~must be provided for synchronizing the
27 sending and/or receiving of the video and audio
28 signals at ~he received end. In conjunction with
29 the more rapid transmission of video images, the use
of known data compression techniques is mentioned in
31 this patent . Similarly, in U. S . Patent No.
32 3,873,771 to Kleinerman, issued March 25, 1975, and
33 entitled "Simultaneous Transmission of a Video and
34 an Audio Slgnal Through an Ordinary Telephone
~ WO 95/34167 2 1 9 2 3 4 1 F~ r~
Transmission 1ine", a communication system is
2 disclosed for transmitting video and audio
3 information using separate bandwidths of the limited
4 bandwidth of an ordinary telephone line. With
regard to the transmission of video information, it
6 is accomplished using slow scan IV techniques so
7 that an image is not transmitted in real time, but
8 rather the transmission requires up to about 8
9 seconds to transmit an image with 120 scan lines per = ==
image.
11 In another technique for transmitting video and
12 audio signals, two signals are multiplexed in such a
13 way to enable one of the two signals to be sent when
14 the other of the two signals is not being
transmitted.
16 These prior art systems are not capable of
17 transmitting, in real time, the audio and the moving
18 video image data together over an ordinary voice =~
19 grade telephone line. Such prior systems require
from about 3-60 sec4nds to transmit a still image.
21 This occurs because voice grade telephone lines
22 typically have a bandwidth of only about 0-3600 Hz.
23 Because of this limited bandwidth, the amount of
24 data or information that can be transmitted in a
given time is limited. To overcome this drawback,
26 it is known to u~e transmission lines, other than - --
27 ordinary telephone lines, for transmitting voice and
28 video data. In such systems, transmission lines are
29 used having a significantly greater bandwidth than
3 0 that of ordinary telephone lines, such as f iber
31 optic lines . With regard to f iber optic
32 transmission lines or other transmission lines
33 having a much greater bandwidth than the ordinary
34
Wo95/34167 2 1 923 4 ~ J~
telephone line, it is known to transmit video and
2 audio signals in real time.
3 Simultaneous tr~n~ s~ on of three television
4 signals i9 disclosed in U. 5 . Pat . No . 4, 593, 318 to
Eng et al., issued June 3, 1986 and entitled
6 "Techni~ue ior the Time Compression Multiplexing of
7 Three Television Signals". In one ~ t oi the
8 system, a time compression multiplexing technique
9 enables the transmission of three color television
signals through a satellite transponder having a 36
11 MHz bandwidth in which one field signal and two
12 field differential signals are each time compressed
13 to permit all three signals to be sent in the period
14 of a normal f ield signal of a standard TV signal .
Since there are three TV sources, with each
16 producing stereo audio, six audio signals are also
17 transmitted. The stereo audio from each source is
18 sent along with the video by inserting digital audio
19 in either the vertical or horizontal bl Ank;
periods associated with the video.
21 In addition to providing an increased bandwidth
22 in order to transmit a plurality of signals
23 including video ~ and audio signals, as some of the
24 prior art indicates, data compression techniques are
employed BO that compressed video information can be
26 transmitted for subsequent ~n~; nn at a receiver
27 6tation, without meaningful loss of transmitted
28 information. Various compression methods have been
29 suggested for transmitting video image data over a
digital tf~ r~,~n~ line. To achieve the compression,
31 spectral, spatial and temporal compression
32 techniques are employed. These data compression
33 techniques are utilized in such a way to exploit the
34 human eye' s forgiving nature so as to make the
~ WO 9S/34167 2 ~ 9 2 3 4 1 r~ "~l.. r~c ~
tradeoffs that cause the least objectionable losses
2 in picture quality. In rnnn~ctlnn with the
3 compression, comparisons are made between new pixel
4 information and previously transmitted pixel
information 80 that only video information that is
6 changing need be sent.
7 Other U.S. patents that use t~lPrhnn~ lines for
8 the transmission of video data can be seen in U. S .
9 Patent No. 5,164,980 for a video telephone and in
Patent No. 5,202,951 for a ~ull Motion Video
11 Telephone System. U.S. Patent No. 3,702,899 for a
12 Digital Video Transmitter uses a conventional
13 tF~ rhnn~ system. U.S. Patent No. 3,974,329 is for
14 the Transmission of Video Pictures at audio
frequencies. Two U.S. patents to Yurt et al. No.
16 5,253,275 and No. 5,132,992 each teach an audio and
17 video transmission and receiving system. U. S .
18 Patent No. 4,620,217 for a standard transmission and
19 recording of high resolution television separates
the modulation frequency as sidebands with pixel
21 information out from the video signal from the
22 television camera. A heterodyne converter is used
23 to convert the sidebands down to a color subcarrier
24 band.
The Gitlin et al patent, No. 4,924,492, is for
26 a method and apparatus for wide band transmission of
27 digital signals between, for example, a telephone
28 central office and customer premises and uses a
29 telephone local loop transmission arrangement in
which data is communicated from the customer~ s
31 premises to a central office ut;l;7;nr~ a multi- =
32 dimensional pass-band signal . In the U. K. patent
33 application, GB 2,173,675A, a ~ ;r~t;on system
34 for sending video and audio signals to a telephone
W09S/34167 2 1 9234 1
line supplies a digitized video signal from a~ camera
2 and uses an analog-to-digital converter along with a
3 frame storage and a parallel-to-series converter.
4 The signal bytes from the converter and sync signals
from a timing generator are supplied to a freS~uency
6 shift keyer to produce an output signal at any one
7 of several distinct frequencies within the audio
8 frequenc~v band of the telephone line.
9 In summary, many systems have been proposed or
devised for transmitting video information and/or
ll audio information over t~l ~rhnnf~ lines but none has
12 been provided that relatively inexpensively sends
13 and receives, in substantially real time, both video
14 informatiQ~and audio information over an ordinary
voice grade telephone line. It would be
16 advantageous to have such a system in order to
17 provide real time viewing.
18 In contrast to the prior art, the present
19 invention allows the tr~n~~; RR; on of real time video
signals over twisted pair copper telephone lines in
21 which monochrome composite color signals are phase
22 modulated relative to a fixed frequency reference
23 tone in the audio frequency range to form a narrow
24 passband, such as 100 Xz. The phase modulated
signals are~; phase detected between the reierence
26 tone and the modulated video signal tQnes and have
27 been converted to a constantly varying phase
28 modulated signal in an audio frequency spaced from
29 the reference tone by a small D(~ voltage, i.e. about
0.17 volts. The system is relatively inexpensive
31 and sends and receives, in real time, both video
32 informatio~ and audio information over ordinary
33 voice grade twisted pair telephone lines and is
34 transmitted through al:l types oi lines including
~ WO95/34167 2 l 923 4 1 i~ C 7~ :~
fiber optic lines and through 51 Prtriri~l switches
2 and repeaters. The present invention i9 further
3 directed to increasing the rate at which data can
4 pass-through a transmission medium so as to increase
the distance over which high bandwidth signals can
6 be transmitted in a low bandwidth medium. This
7 increase of the apparent bandwidths of a
8 transmission medium include low bandwidth telephone
9 lines and cable as well as fiber optic lines and
broadcast over the airwaves as well as a
11 communication satellite link. In one specific
12 embodiment of the invention, monochrome or RGB color
13 signals are transmitted over a low bandwidth
ls telephone line or other communication link over
substantial distances with a minimum degradation
16 thereof. The transmission of the video signals can
17 be over conv~nt; nn~l telephone lines through an
18 existing telephone system including an international
19 communication link over large distances, such as
several thousand miles, with no modification of the
21 t~ hnn~ system or line and with only partial
22 degradation of the picture ~uality. In addition,
23 the video signals can be pa~sed through the
24 conventional switching equipment of telephone
exchanges and through the conventional repeaters
2 6 used in telephone lines without rej ection as high
27 f rer~uency noise . The present invention also
28 provides an improved encoder and decoder for the =
29 transmission of stored information including a
variable reference line for referencing phase
31 modulated data which is phase detected through
32 operational amplifiers or the like to provide a high
33 sensitivity to the predetermined freriuency and which
34 detectors can operate to drive a voltage controlled
W095134167 21 ~2341 r~ cr-~7~ ~
frequency conver~er circuit to produce frequency
2 input to the encoder. Another il~ JY~ ' t in the
3 present invention includes the transmission of high
4 bandwidth signals over a long distance in a low
5 bandwidth transmission medium util;7;n~ a very low
6 signal level in an area below the level of the
7 telephone f ilters that reduce noise on the telephone
8 line. It is also a purpose of the present invention
9 to be able to use the encoded data placed directly
10 on a storage medium, such as an optical disc storage
11 or magnetic storage, such that large amounts of data
12 are stored o~ the storage medium in the erlcoded
13 format which can be decoded by a decoder.
14 It will be understood by those skilled in the
15 art that a communication link or data channel is a
16 path for transmission between two or more stations
17 or t~rm; n~l 5 and it can be a single pair of wires or
18 a group of wires in a cable, a coaxial cable, or a
19 fiber optic cable, or a special band of the RF
2 0 spectrum . The system advantageously can be used
21 interactively in real time. Digital data is
22 generally used in place of analog information in
23 electronic and computer applications eo that data
24 communications is the electronic tr~nRm; Rsion of
25 encoded information or data from one point to
26 another. The present invention lt;1;7~R phase
27 modulation. Phase modulation is the phase of the
28 carrier wave is varied by an amount prop~rtional to
29 the amplitude of the message signal. In phase
30 modulation, the inst~nt~n~nus phase o~ the carrier
31 is shifted i~ accordance with the modulating
32 waveform. The extent of the phase shift is airectly
33 proportional to the amplitude of ~he modulated
34 signal . The rapidity of the phase shif t is directly
~ Wo95134167 21 ~2341 r~ c.~
proportional to the change in the amplitude and
2 frer~uency of the modulating signal.
4 SU~ARY OF T~IE INVENTION
6 The present invention relates to the
7 transmission of i~formation over a communication
8 link, such as a telephone line, and to the storage
9 of such information and to a system for transmitting
lO real time video images over a twisted pair telephone
11 line or communication link of any kind. The
12 apparatus includes a data encoding circuit having a
13 tone generator for producing a fixed frequency tone
14 within an audio freriuency band and a harmonic
15 generator for phase modulating an audio frequency
16 that is spaced in amplitude from the reference tone.
17 The composite signal thus generated is applied to a
18 c, ; r~tion link where a remote decoder has a
19 phase detector circuit driving a voltage controlled
2 0 f reriuency conversion circuit to decode the data f rom
21 the audio f reriuency and reproduce the original high
22 frer~uency signal8. The encoded data in a preferred
23 embodiment is applied to the communication link with
24 a very low level signal having an amplitude of less
25 than -32 dbm (relative to 1 mw~ and can transmit
26 video signals real time over existing telephone
27 lines and over any communication link. The method
28 of the present invention includes generating a iow
29 frer1uency reference signal and a low frequency
30 modulated data signal from a modulated high
31 frequency data signal, which signals are
32 superimposed one over the other, and then combining
33 the signals for the tr~nF"'; ASl on over a
34 communication link at a very low level, such as
WOgs/34~67 21 92341 r~
between -40 and -60 dbm and in a frequency range
2 between 10 and 3600 Hz. The process also includes
3 phase ~t~ct 1 nrj the combined signals at a remote
4 receiving station to drive a voltage controlled
frequency conversion circuit to thereby produce an
6 output of high frequency modulated data from the
7 transmitted data signals received over a
8 communication link. The encoded signals can be
9 applied to a storage medium where they can be
decoded at a later time with a decoder circuit, for
11 example, playing on a video monitor. The
12 transmitted or stored 6ignals are i~ eifect
13 compressed and allow large amounts of data to be
14 transmitted through a narrcw audio frequency band,
such as less than 100 ~z 80 that a large number of
16 separate bands can be simultaneously transmitted
17 over the same communication link.
18
19 ~RT~ nTi~.~('RTPTIO~ OF TTT~: DRA~INGS
21 Other objects, features, and adva~tages o~ the
22 present invention will be apparent from the written
23 description and the drawings in which-
24 Figure 1 is a block diagram of a basic system
for encoding, transmission, and ~ rt~1;n; data in
26 accordance with the present invention;
27 Figure 2 is a waveform diagram;
28 Figure~3 is a schematic diagram of a preferred
29 embodiment of the encoding circuitry oi- the present
3 0 invention;
31 Figure -4 is a schematic diagram of a preferred
32 embodiment of the decoding circuitry of the present
33 invention;
34
W0 9sl34l67 ;~ ~ q 2 3 i l F~l/lJ.. 51
Figure 5 is a schematic diagram of a
2 tr~nFm; q~ion circuit for transmitting video signals
3 over a telephone line; and
4 Figure 6 is a schematic diagram of the
receiving circuitry for receiving and ~c-.-l;n~
6 transmitted video signals transmitted over a
7 telephone line.
9 DESCRIPTION OF THE ~ ~k~ EMBODIMENT
11 Referring to Figures 1 and 2, a basic
12 embodiment of the invention is illustrated in the
13 block diagram of Figure 1 with the input waveform
14 illustrated in Figure 2. In operation, a data
15 signal, which is an intelligence carrying signal,
16 and which may, for instance, be a television or
17 video composite signal, is input at 10 into an
18 encoder 11. The encoder is a reference tone
19 generator and encoder which produces from the
20 modulated signal 10 a composite signal from a fixed
21 frequency reference signal 12 and a modulated data
22 signal 13 shown superimposed on the fixed frequency
23 tone 12 to form a composite signal. The signals 14
24 and 12, shown relative to each other in Figure 2,
25 are ~ I-,mh; n.ocl to form a composite signal for
26 ~r~n~ sion. The composite signals are thus the
27 combined fixed frequency reference signals 12 and
28 the continuously phase modulated data signal 13.
29 The fixed frequency signal 12 acts as a reference
30 signal relative to the modulated signal 13 much as a
31 conventional signal will be referenced to a zero
32 voltage line. The modulated data signal 13 thereby,
33 at any instance, has a phase relationship between
34 the modulated portion of the signal 13 at any one
WO95/34167 21 9 234 l r~ c~
point, such as 15, relative to the adjacent point 16
2 on the fixed frequency tone but the phase
3 relationship i9 constantly changing as the signal 13
4 i8 modulated. The composite of the Eignals i8
transmitted over a communications link 17, which can
6 be an ordinary twisted pair telephone~ line, but can
7 also be any other communications link desired.
8 The signal being transmitted over the
9 communication link 17 is detected by a phase
~ circuit 18 at a remote location. The phase
11 detector in this case may be an operational
12 amplifier ~or OP amp) which receives the composite
13 signal and, by constantly reading the phase
4 difference-between the composite signal components
12 and 13, --produces an outpu~ of a continuously
16 varying D~oltage signal in the output line 20,
17 which cu ~ ullds to the modulated signal of the
18 input 10. The constantly varying DC voltage signal
19 20 is applied to a voltage controlled frequency
conversion circuit 21 which, for instance, may be a
21 voltage controlled oscillator, so that each voltage
22 level being impinged upon the circuit 21 produces a
23 predetermined output frequency in the output 22
24 which is identical to the modulated signal of the
input 10 at the remote encoder. The frequency
26 conversion circuit 21 can be any voltage controlled
27 frequency conversion circuit desired and utilizes
28 commercially available integrated circuits. The
29 phase detector can be any commercially available OP
amp but it~is desirable to have a more sensitive
31 amplifier for detecting very low amplitude signals
32 14 The operational amplifier is also set to detect
33 only signals within a narrow frequency range
34 ~ cSing the composite signal The detector is
21 q2341
WO 95134167 . ~~ 7
13
strapped by a resistor value to a specific reference
2 tone 80 that it is looking to the specif ic
3 transmitted reference tone. This rejects noise or
4 other interferences with the signal from being
transmitted. The encoder 11, which produces this
6 signal, includes a tone generator which accurately
7 produces the stable fixed frequency signal tone 12.
8 The encoder 12 circuit can also take a higher
9 frequency, such as a video signal input, and convert
it to a phase modulated signal 13 spaced by a
11 predetermined, but small, level from the reference
12 signal 12. The voltage difference between the
13 signals can, for instance, be offset by about 0.17
14 volt. The fixed frequency signal 12 can be an audio
frequency within the range 10 to 3600 Xz so that the
16 signal can be transmitted through a twisted pair
17 telephone line 17. It has been found that the
18 circuit 11 can use a commonly available integrated
19 circuit chip, such as a phasing chip, when modified
with a feedback loop which makes the reference tone
21 12 fixed at a very stable frequency and which
22 eliminates reference tone harmonics being created by
23 the circuit.
24 The composite signal can be applied to a
communication link 17 in which the communication
26 link includes a twisted pair t~l~rh~n~ line. Thus,
27 large amounts of information can be transmitted when
28 the level of the tone signal 12 is very low, such as
29 below -32 dbm (relative to lmw). The encoder
reduces the signal level with a resistor value set
31 to a level below -32 dbm. Current work indicates
32 that an optimum signal level for use on telephone
33 lines is between -40 and -60 dbm. However, the
34 optimum level range results from the fact that
WO 9~/34167 2 l 9 2 3 4 ~ r~
14
signals above -40 dbm are filtered out on telephone
2 lines and bf~cause the equipment rises rapidly in
3 cost and complexity below -60 dbm. ~Iowever, it has
4 been shown that the signal can be transmitted below
-60 dbm and theoretically can be transmitted well
6 below this level.
7 As can be seen from the basic circuit, the
8 transmitting of large amounts of information in the
9 composite signal 14 uses a very small bandwidth on
the order o 100 Hz. The fixed requency reerence
11 tone 12 for use on a telephone line is chosen
12 between 40 and 3600 Hz of the audio range and with
13 an amplitude of less than 200 millivolts and thus
14 can transmit a very large amount of information to a
remote source. The signals at this low level have
16 been found to pass through t~l.ophnn.- lines of all ::
17 types, twisted pair and fiber optics as well as
18 through the phone company switches and repeaters and
19 through r .ol l ~ r phone cnnnf~ctinnc.
Turning to Figures 3 and 4, a schematic diagram
21 of a circuit in acrnrl~nr,o with the present
22 invention is shown.
23 In Figure 3, an encoder circuit 23 in
24 accordance with the present invention includes a
reference tone generator 24 and a frequency
26 multiplier or harmonic generator 25. The reference
27 tone generator is wired around an amplifier 26
28 having a feedback loop to produce the reference tone
29 12 in its output line 27. Reference tone 12, as
3 0 shown in Figure 2 I may be a f ixed f requency sine
31 wave in the audio range between 40 and 3600 Hz but
32 will work at higher fre~uencies on a transmission
33 media, such as fiber optic lines. A tone generator
34 24 puts out a different frequency reference tone for
~ WO 95/34167 2 1 ~ 2 3 4 1 ~ c ~
each transmission band. The harmonic generator 25
2 i5 illustrated using three gating amplifiers IC1, -~
3 IC2, IC3 and has an input 28 for feeding a high
4 frequency input, such as a composite video signal,
or the like thereinto. The reference tone on the
6 line 27 from the reference tone generator i5 applied
7 at the opposite input to ICl and IC2 from the input
8 28. The harmonic generator 25 is keyed to phase
9 modulate the high frequency input at 28 to produce a
phase modulating signal 13, as shown in Figure 2.
11 The phase modulating signal 13 as illustrated is
12 produced as a modulated signal tracking a sine wave
13 which is slightly biased above the reference tone
14 12. The bias between the reference tone 12 and the
modulating frequency 13 may be about 0.17 volt
16 between the fixed frequency 12 and the average of
17 the modulating sine wave 14 between points 15 and 16
18 or, in any event, the bias is set for less than 0.2
19 volts. The circuit 23 has an output 30 which has
combined the fixed frequency tone 12 and the
21 modulating signal 14 into a composite signal, which
22 composite signal is being outputted on the line 30
23 for transmission on a communication link or for
24 storage for later tr~n~ ; on or playback as
desired. In tr~nr~ ; on over a communication link,
26 the composite data signal at the output 30 is at a
27 level of less than -32 dbm and preferably in a range
28 between -40 and -60 dbm. Signals at this level
29 would normally be considered in the noise level but
have been found, when modulated in this manner, to
31 pass through twisted pair copper telephone lines
32 without stripping the modulated signal portion 14
33 from the composite signal.
34
WO 95~34167 r~ c ~
21 9234l
16
The circuit components values in Figure 3 are
2 as follows:
3 Rl = lOkS2
4 R2 =-lOkQ
5 R3 = 1. 5meg Q
6 R4 = lOmeg Q
7 R6 = 20kQ
8 R7 = 510kS2
g R8 = 3 . 3meg
R9 = 3.3mn
11 R10 = 7 . 5k
12 Rll = 5 6k or
13 Cl = 471Lf, lOOv
14 C4 = lOO~Lf
C5 = lOO~f
1 7 C 6 r 6 . 2 ~L f
18 Referring to Figure 4, the output 3Q from the
l9 circuit of Figure 3 is received on the incoming
20 telephone line 31 of the decoding circuit of Figure
21 4 where it is applied to a phase detector circuit 32
22 having an ~C chip NE5210 wired as a phase detector
23 when received from the communication link 31 through
24 the capacitor C7. The integrated circuit 5210 is a
25 circuit formed of a plurality of operational
26 amplifiers wired to provide a narrow bandwidth for
27 the received phase modulated signal on the line 31.
28 Alternatively, a single operational amplifier can
29 also be wired to detect the phase modulation by
30 separating the tone reference 12 of Figure 2 and the
31 phase modulated signal 13, which has been combined
32 in the composite signal. The circuit 32 provides a
33 stable and very sensitive phase detector.
34 The output from the inte~rated circuit 32,
35 through the lines 33 and 34, are applied to a DC
36 stabilizer circuit 35, using either a MC1596 or an
37 MC1496 IC. -This circuit is a monolithic transistor
38 array arranged as a h~l ~n~P~ modulator/~lP~ tor
39 and generally is selected because o the P~'Pl 1 Pn~
W095134167 L 1 9 234 1 P~ C~
matching qualities of monolithic devices to provide
2 a superior carrier and signal rejection. The
3 versatility of the balanced modulator chip of this
4 type allows the device to be used as a phase
detector or as a DC stabilizer to further enhance
6 the signal from the phase detector 32. The two
7 signals on the lines 33 and 34 can be DC signals
8 analogous to the signals 14 of Figure 2 so that the
9 different components become stabilized time varying
DC and any undesired sum components are filtered
11 out. The output DC component is related to the
12 phase angle and provides an improved linearity of
13 the converted signals while at the same time
14 providing a conversion gain for greater resolution.
The output from the circuit 35 is applied to
16 the IC chip 36, an AD652 AQ chip, which is a voltage
17 controlled frequency conversion circuit which
18 converts DC inputs on lines 37 and 38 into a
19 continuously varying high fre~uency at the output
40. This frequency output should be the same as the =~
21 high frequency input 28 from Figure 3 and is a wide =:
22 band high frequency output. The fre~uency
23 conversion circuit 36 could be a voltage controlled
24 oscillator chip which continuously converts the DC
voltage input on the lines 37 and 38 to a
26 ~nnt;nllnusly ~ nging fre~uency analogous to the DC
27 voltage input.
28 It has been found that when the encoder of
29 Figure 3 puts out a composite signal from the
3 0 component signals of Figure 2, with a very low
31 amplitude o~ below -32 db, the signals can be
32 transmitted through twisted pair copper telephone
33 wires as well as other telephone lines and
34 transmission media carrying information from the
WOg~/34l67 2l 92341
18
input high frequency signals in the input 28. The
2 transmitted signals can be detected and can produce
3 a color or monochrome video signal at the output 4 0
4 which can operate a monitor in real time from the
5 input signal 28. The decoder circuit o~ Figure 4 is
6 able to detect and reproduce the signal transmittea
7 over such a communication link at great distances
8 without any significant loss of signal, with the
9 signal transmitted in an audio ~requency band of
between 40 and 3600 Hz, and with a plurality of
ll signals transmitted in an audio bandwidth of 100 Hz
12 or less. The signal can also be transmitted over a
13 higher fre~uency, above 3600 Hz, where there is not
14 a twisted pair telephone line in the communication
15 link. Thu~, a large number of video signals can be
16 transmitted simultaneously over a single twisted
17 pair copper telephone line and can transmit such
18 video signals through multiple transmission media,
19 such as fiber optic lines, tPlPrhnnP company
20 switching stations, and various types of high speed
21 switches as well as through telephone line repeaters
22 incorporatea into the telephone lines without any
23 reduction i~ the signal. Raising the signal output
24 at the output 30 of Figure 2 above -32 dbm presently
25 results in the tP1 erl~nnP company filters filtering
26 out the ,~ AtP,l signals. Also, raising the signal
27 level above this point substantially reduces the
28 transmission efficiency.
29 The circuit, , ^nt valves in Figure 4 are as
30 follows:
31 R12 = 5 6kn
32 R13 = 5152
33 ~ R14 = 51n
34 R15 = 5 . 6kS2
R16 = 5.1meg Q
WO95134167 2 l 9 2 3 ~ . 7~
19
R17 = 3 . 9kQ
2 R18 = 3 . 9kQ
3 R19 = lkQ
4 R2 0 = lkQ
5 C7 = 1 . 411f
6 C8 = . l~f
7 C9 = .47,Lf
8 C10 = . lllf
Figure 5 shows a schematic diagram of the
11 present invention using commercially available
12 integrated circuits in an embodiment of the encoding
13 and reference tone generation circuitry. A
14 composite video signal is received on line 100 which
signal may be generated by a video camera, video
16 tape, or from disc storage or the like. The signals
17 are applied to the video jungle circuit 101 which
18 provides separation of the signals into separate R,
19 G, and B signals. The video iungle integrated
circuit (NTE 1473) contains a self-regulating power
21 supply and the ability to process composite video
22 into the separate red, green, and blue signals, and
23 the ability to supply lumina and sync, and is
24 crystal controlled. The circuit is commercially
used in many television receivers. ~ quartz crystal
26 element 102 controls a clock circuit for applying a
27 signal to the video jungle circuit 101. The signal
28 output from the video jungle circuit 27 includes RGs
29 signals applied to lines 103, 104, and 105 which in
turn apply the respective signals to the encoder and
31 reference tone generator circuits 106, 107, and 108.
32 A lumina output signal on the line 110 is applied to
33 an encoder and reference tone generator 111 for
34 producing a composite signal having a fixed
frequency modulated reference tone and a spaced
36 phase modulation data signal. Each of the encoders
37 and reference tone g~n~r~ rs produce a low
2 1 9234 1
W095134167 F~ c-~
frequency reference tone in the audio frequency
2 range between 40 and 3600 Hz in which each reference
3 tone can typically be separated by 100 Hz. 13ach
4 reference tone is either one of the RG~3 signals or
5 the lumina eignal encoded in a phase modulated
6 synchronization signal in a low frequency stream
7 over one rel~erence: tone as seen in the waveform of
8 Figure 2. ~3ach of the reference tones from the
9 encoder and tone generators 106, 107, and 108
10 produces a composite output signal with continuously
11 varying phase difference between the video signal
12 portions from the video jungle circuit and the fixed
13 frequency modulated reference signal. The composite
14 signal for the signals is a phase differential
15 signal used in transmitting the signal over a
16 telephone line 112. The phase difference ~ignal of
17 the lumina signal is applied to line 113. The
18 circuit r~ ~ nnf~nt values in Figure 5 are as follows:
19 R1 = lOQ
R2 = lkQ
21 R3 = 470n
22 R4 = 560n
23 R5 = 270n
24 R6 = 56kn
2 5 R7 = lk
26 C1 = . 331~f
27 C2 = . 0082~f
28 ~ C3 = 30~f
29 C4 = lOO~Lf
C5 = . 008211f
31 __
32 The signals from this circuit are applied over
33 the telephone line 112 to the receiving circuit in
34 Figure 6 where the signals are first received by a
35 series of detectors which may operational amplifier
3 6 integrated circuit 114 which produces the phase
37 detected signals on the lines 115 and 116 to a
33 voltage cor~rolled.o~ tr~r or VCo circuit 117.
~ WO95/34167 2 1 9 23 ~ 1 P~ c~
21
The signals are also appliea from the input line 118
2 to a circuit 120 which detects the phase shift in
3 the eignals between the data carrying signals and
4 the fixed frequency reference tone and produces a
varying DC signal output. The detector circuit 120,
6 which is also an OP amp is limited to a narrow
7 bandwidth to generate a frequency and amplitude
8 signal which is then applied over the circuit lines = -
9 121 and 122 to a VCO 123. A third signal, . ~-n~nt
received over a telephone line 118 is applied to a
11 third detector or operational amplif ier 124 which
12 generates a varying DC output on the circuit lines
13 125 and 126 to the VCO 127 which generates a -~
14 continuously varying frequency responsive to the
varying DC voltage applied thereto on the output
16 line 128. The output from the VCO 123 is on the
17 line 130 while the output from the VCO 117 is
18 applied to the line i31. In addition, signal
19 components from the telephone line 118 are applied
to the detector operational amplifier circuit 132
21 which applies its output signal to the circuit
22 conductors 133 and 134. The signals are applied to
23 a VCO 135 which has an output onto line 136. A
24 composite of all the outputs is applied as a
composite video signal at 137 where it may be
26 applied to a video monitor, producing a composite ~=
27 high resolution television eignal, with scan lines
28 in accordance with the National Television Systems
29 Committee (NTSC) standards for television
30 transmission, and which may also be detected by a
31 monochrome receiver to display the image in black
32 and white. The eignals, of course, can be
33 transmitted in accordance with other standards, such
34
WO 95134167 2 19 2 3 $ 1 r~ 7~ ~
as PAL or SEACAM. The circuit component values in
2 Figure 6 are as follows:
3 R8 = lkQ
4 R9 = lkQ
~ C7 = 331lf (kov)
6 C8 = . 08211f
8 It should be clear at this point that the
9 process and circuity for the transmission of video
10 signals Ovæ a communication link, such as a
11 telephone line, have been provided. The process
12 includes the step of generating a composite video
13 signal for :transmission to a remote point, such as
14 with a video camera or the like, changing the
15 composite video signal frequency to a lower
16 frequency applied to and spaced apart from an audio
17 reference signal. The composite video IC signal is
18 separated into a plurality of component signals in
19 the embodiment of figures 5 and 6 A plurality of
20 separate audio re~erence tones are generated in the
21 audio range, each being slightly different in
22 frequency from each other, such as by 100 ~z, with
23 each reference tone having one component of the
24 separate composite video signal applied thereto.
25 The measured phase differences between each
26 component video signal and the re~ereIlce tone is
27 transmitted in a composite signal.
28 The method includes the receiving of the
29 transmitted composite audio reference tone and
30 separated audio/video signals at a remote location
31 and then recons~ituting the composite video signals
32 to produce a video signal transmitted in real time
33 over a telephone communication link including an ~~ ~
34 ordinary twisted wire t~l ~rl~n~ line. The composite
35 signal is applied to the tF~l o~ n~o line at a very
09sl34l67 21q2341 P~ J,.,S'C'7
low amplitude, such as below -32 dbm and preferably
2 in the range of between -40 and -60 dbm.
3 It 3hould be clear at this time that both a
4 method and circuit have been provided for encoding,
transmitting, storing and decoding information in
6 signals, and can transmit video signals over voice
7 grade telephone lines, as well as large amounts of
8 analog and digital data. The signals transmit
9 equally well over other telephone lines, including a
typical mix o~ twisted wire and fiber optic cable
11 and through the line switches and repeaters without
12 loss of signals. The signals can also be stored by
13 later decoding and in this oonn~rt; on allow the
14 storage o~ large volumes of data in a limited space.
However, the present invention is not to be
16 r~ red limited to transmissions over telephone
17 lines since the signal can be stored in disc or :~
18 magnetic memory which then in effect becomes a very
19 compressed form of storage. The signals can also be
transmitted over a satellite link and digital data
21 as well as analog have been found to transmit over
22 the communication3 link. Accordingly, the ~orms
23 shown are to be considered illustrative rather than
2~ restrictive.
