CA1295728C - Transmission device, notably video signals - Google Patents
Transmission device, notably video signalsInfo
- Publication number
- CA1295728C CA1295728C CA000557783A CA557783A CA1295728C CA 1295728 C CA1295728 C CA 1295728C CA 000557783 A CA000557783 A CA 000557783A CA 557783 A CA557783 A CA 557783A CA 1295728 C CA1295728 C CA 1295728C
- Authority
- CA
- Canada
- Prior art keywords
- signals
- line
- current
- impedance
- generators
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/10—Adaptations for transmission by electrical cable
- H04N7/108—Adaptations for transmission by electrical cable the cable being constituted by a pair of wires
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
Abstract
ABSTRACT OF THE DISCLOSURE
A transmission device for signals, notably video signals, between at least one transmitter assembly and at least one receiver assembly by means of a two wire connecting line, equipped at each end with a symmetrical transformer and fed by at least one current generator; the generator delivers symmetrically on the wires and is controlled in voltage by the signals to be transmitted, having a frequency between 50 Hz and 30 MHz, the line being adapted at each end by an impedance equal to its characteristic impedance.
A transmission device for signals, notably video signals, between at least one transmitter assembly and at least one receiver assembly by means of a two wire connecting line, equipped at each end with a symmetrical transformer and fed by at least one current generator; the generator delivers symmetrically on the wires and is controlled in voltage by the signals to be transmitted, having a frequency between 50 Hz and 30 MHz, the line being adapted at each end by an impedance equal to its characteristic impedance.
Description
5~7213 Field o-f _he Inventio_ The present invention is a device for -the remote transmission of signals, and in particular video signals, by two leads of smal:L diame-ter, not sheathed, which can be easily pu-t in position, notably be-tween two locations or -two existing installations, separated from one ano-ther.
Background of -the Invention Many signal and/or data transmission devices between two distant points separated by a de-termined distance are already known in the art. In particular, many systems using connec-tions by coaxial cables or transmission lines called "buses" are known. However, with these standard systems, and when the task is to transmit video signals, it is generally necessary that said signals are frequency or amplitude modulated and that they do not remain in the baseband if one wishes to avoid a quick degradation of said signals, which is all the more important as the diameter of the coaxial cables used is smaller. With cables of large diameter, the degradation of the signal is less but the instal-lation is costly and above all less convenient. The problem is forming passages in the walls through which the large diameter cables are to pass to provide con-nections with the equipment at said locations. Forcables of smaller diameter, a frequency or amplitude modulation of the signals is always necessary, thereby making necessary the use of a modulator and then of a demodulator, introducing some distortion and limi-tations. Moreover, some of said systems designed forlong range transmission of signals from the output of a tape recorder or those which are to be applied to the input of a television set of a known type, and using the demodula-tor present in the standard -television sets, are incompatible with the use of simple visuali-2~3 zation moni-tors.
The present invention is a device allowing the -transmission of at least one signal, such as but no-t limited to a video signal, maintained in the base-band without modulation. The device is reliable,simple -to produce and allows transmitting a signal without disturbing it, wi-thout this signal disturbing the environmen-t, or without being itself disturbed by said environment. The device also has a wide pass-band, excellent linearity and a signal/noise ratioremaining satisfac-tory across said band.
More particularly, the invention is directed to a transmission device which allows transferring signals corresponding to information of any nature and of the type which can be found in many industrial as well as domestic applications. Thus, in the case of hotels and communities for example, the presen-t device allows advantageously communication from a given cen-tral station, or more generally between several sta-tions. The present device can transmit various tele-phonic, radio, or television messages, information relating to security, the supervision and the eventual control of inlets and outlets, the change of codes or door locks, and the usage of some sexvices, wake-up calls, etc. In such applications, it is obvious that when the account of information that can be transmitted by leads of small section becomes more important, the multiplication of unaesthetic and bulky cables and the disadvantages due to setting them in place increases in proportion. The limitation to the twin-wire line of the invention, each having a diameter which can be no-tably less than 1 mm, allows easy passage of the lines underneath washboards, be-tween floor planks, underneath doors, and underneath carpets. This is a great advan-tage particularly in homes or hotels.
On the other hand, in the video and trans-, .., ~
. . .~, ~ ., I I, mission of television images field, i-t is known that said images come more and more frequently from various sources, notably tape recorders, cameras, converters of signals transmitted by coaxial cables or optic fiber beams, video disc readers, and television sets. The problem is establishing communication upon request from each of said sources at will with other receivers or moni-tors at the disposal of the users. Outside even the hotel or community field, for exarnple a simple domestic usage, one can easily imagine the possibility of establishing inside the same home a transmission assembly, possibly connected with an audiophonic assem-bly, allowing a remote -transmission from one room -to the other of the television images accompanied by sound signals and also remotely controlling the sources of said signals.
The present invention is therefore directed to a multi-input transmission device for conveying signals, such as video signals, but possibly of an 2Q other nature, which can be transmitted according to the standards of any system (SECAM, PAL, NTSC, D2 MAC PAQUET ...) and are from any appropriate source (a receiver for a ratio transmitter, a receiver antenna for transmissions from satellites, cables, etc. The device avoids the use of bulky and costly transmission coaxial cables that are liable to introduce interfer-ence in the various signals transmitted, especially if the cables are of a great length.
Transmission systems using two leads of small diameter are certainly already known. Thus, FR-A-2 584 555 refers to a wide band signal transmission device in a network, possibly of video-communication with a star-shaped structure, where the video infor-mation can be remotely transmitted to a plurality of distinct receiving sets. In such systems, the signals to be transmitted are adapted in an input equipment and e~
transmitted -to an output equipment via a balanced and symmetrical twin-wire line -through a switching matrix including M lines and N columns interconnected, the matrix being associated with an address memory allowing selection of the chosen switching address. Finally in said systems, the transmitted signals are filtered in the input equipment so as to separate the low and high frequency components, each of which being the object of a transmission on the twin-wire line according to a different mode. Regarding the high frequency compo-nent of the signal, it is sent in a differen-tial mode through a transformer, the two components going, in the outpu-t equipment, through a summation device for reconstituting the signal. Such a device is costly, complex and risks introducing signal distortion wi-th a poor signal/noise ratio, above all if the frequency band is made relatively wider.
With respect to the prior art thus shown, the present invention has the advantage of a very simple device, allowing -transmitting in optimal conditlons any signals received at its input, whatever the standard used. With the present device it is not necessary to separate the high and low frequency signals in the signal spectrum, instead said signal can be immediately remotely transmitted in its whole extent by the two leads of the line equipped with symmetrical trans-formers, due to an appropriate adaptation and a balanc-ing of the line avoiding the radiation of said line.
To this effect, the signal transmission de-3Q vice, transmitting signals between at least one trans-mitter assembly and at least one receiver assembly by means of a twin-wire connecting line of small diameter, equipped at each end with a symmetrical transformer and powered by at least one current generator, is charac-terized in that the current generator outputs symmetri-cally to the line and is controlled by the signals to ~, r;
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be transmitted. Said signals generally have a fre-quency between 50 Hz and 30 MHz and the line is balanc-ed at each end by an impedance equal to its character-istic impedance.
Advantageously, the two identical wires are not shielded and each have a diameter less than or equal to 1 mm, it being understood here tha-t -the in-vention has its essential advan-tages in -the use of leads of small diameter but larger diameter wires can be used. Moreover, although it is obvious that the wires oE the line have preferentially a circular cross-section, they could also be flat, notably in the shape of tapes placed on an insula-ting support or imbedded in said support, without departing from the scope of the invention.
Preferably also, the symmetrical transformers fitting out each end of the two wire lines have mag-netic core with each winding mounted in series with one of the wires of the line. According to a particu-2Q lar embodiment, the windings of the symmetrical trans-formers are themselves made of the line wires. These transformers strongly reduce line noise without damping the high frequency components of the transmitted sig-nals.
According to another feature of the inven-tion, each transmitting assembly includes two current generators, one controlled by a signal and the other by the inverse of -that same signal and delivering sym-metrically on one and the other of the line wires, said 3Q generators being mounted in series with a matching impedance unit having a value which is equal to the line characteristic impedance. Preferably, the imped-ance unit in series with the generators includes resis-tors and a capacitor adapted to separate the continuous component from the signals to be transmitted. More-over, the matching impedance unit is advantageously . ~ .
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7~3 formed by means of two equal impedance uni-ts moun-ted in series and with -the node be-tween -the two units connect-ed to the ground via a capaci-tor. Likewise, in each receiver assembly, the matching impedance unit of the line is mounted in parallel on said line and is as such made of -two equal impedance units mounted in series with a medium point connected to the ground.
According to another advantageous feature of the invention, each receiver assembly includes two current genera-tors supplying the power supply current to said assembly. Moreover, and according to another feature, the receiver assembly includes a complementary current generator, operating symmetrically, with its voltage controlled by modulated signals, distinct frorn those controlling the generators of the transmitter assembly, whereby said signals can be in par-ticular remote controlled signals circulating on the twin-wire line in a direction reverse to that of the signals re-ceived from the transmitter.
Brief Description of Drawings Other characteristics of a signal trans-mission device according to the invention will become apparent from the following description of an embodi-ment, given as an indicative and non limiting example, with reference to the accompanying drawings wherein:
- Fig. 1 is a systematic diagram showing on the ordinate the maximum voltage of a signal trans-mitted as a function of the length of the transmission wires in any line, plotted in abscissa.
- Fig. 2 is a schematic block diagram of the transmission device according to the invention.
- Fig. 3 shows in greater detail the device transmitter assembly.
- Fig. ~ shows also in greater detail the device receiver assembly.
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7'~3 - Fig. 5 is a block diagram of the device which allows to better understand the implementation of the means which also provide, accordiny to the inven-tion, the voltage balancing oE the device.
- Eig. 6 is a diagram of the twin-wire trans-mission line.
Detailed Description of the Invention Generally, it is known from -theory and ex-perience that in a signal transmission installation using a twin-wire line, it is possible to considerably reduce the radiation created by the assembly of the two wires by reducing the dissymmetry of the operation durirlg transmission. The device according to the in-vention basically takes advantage of this observation.
In Fig. 1 is shown on curve 1 the maximum voltage of a signal transmitted as a function of the length of the transmission wires for a glven maximum radiation limit. Curve 1 which is na-turally decreasing shows in practice irregularities if the transmission is not symmetrical, the wires behaving as an antenna. On said same Fig. 1 is shown by curve 2 the influence of the voltage created by the interference due -to the outer electrical field on the line, also as a function of the wire length.
One can thus establish that this influence increases substantially linearly when -the transmission wire path is rectilinear. On the contrary~ if said wires follow complex paths, which is generally the case in applications of interest where the signals have to be transmitted between two distant locations by the line following an appropriate path which conceals it as best as possible, curve 2 becomes complex since its slope depends on very many factors and particularly on the frequency of the outer field and on the shape of said field. One infers therefrom that for better z~
-transmission it is advantageous -that the intersection point 3 of curves 1 and 2 be as remote as possible from the abscissa axis for a more efficien-t transmission.
This condition is substantially met when there is a symmetry in -the transmission line. In fact, the greater the symmetry the higher curve 1 is on the diagram of Fig. 1 and the smaller -the slope of curve 2, which permits a greater possible length of transmission without interference. Moreover, -the use of such a sym-me-try in the line avoids the need for shielding for the conducting wires.
Therefore, the present device takes advantage of the hereabove observations. To this eEfect, it in-cludes substantially a transmission line with two wires of small diameter, of the order of 1 mm or less, con-necting a transmitter assembly to a receiver assembly.
Said wires are cylindrical and parallel, maintained in position by an appropriate insulating material. The transmitter assembly includes a variable number of in-2Q puts, adapted to be connected to various signal sourcesand a receiver assembly having the same or a different number of outputs which can be connected to user appa-ratus, receiving and exploiting signals incoming from the transmitter and others arriving on the line. The twin-wire transmission line and the respective trans-mitter and receiver assemblies form the basis of the device. The transmitter and receiver can be mounted symmetrically or be each transmitting and receiving.
Moreover, one can foresee on the line the possible need 3Q for intermediate transmitters or receivers so that a signal can be received and then retransmitted in order to ensure its integrity along the line to other re-ceivers. Likewise, complementary signals which are superimposed on the line with those that are already transmitted by said line can be in-troduced at each intermediate receiver, without interfering with said t~
,. .
57~3 signals and wi-th the operation of the line.
According to the inven-tion, at each end of the transmission line is connected, through symmetrical transformers current generators having their character-istics and control mode chosen according to the inven-tion for ensuring a perfect symmetrical balancing of -the whole assembly. In particular, each current gener-ator is designed in such manner as -to allow sending a signal and/or a current on the line or to take a signal lQ from said line, without modifying the loading impedance value of said line. In the transmitting assembly, the current generators have their voltage controlled in a symmetrical way from the signals to be transmitted. In the receiver assembly, the generators are connected to the ends of -the -transmission wires, preferably and as will be seen hereafter via a diode bridge in order to avoid polarity errors when connecting the wires.
In a most general way, the device is there-fore designed for providing a permanent balancing of the line as regards the direct voltages, particularly by avoiding any possibility of shorts to ground. More-over, at the level of each transmitter and/or receiver, a particular balancing with respect to the line sym-metry is also ensured by means of an impedance unit mounted in series with the current generators, said impedance unit is in turn parallel to the transmission wires in order to form, each time, a circuit where the alternating voltages involved are balanced.
In Fig. 2, the line transmission wires are 3Q respectively designated by reference numerals 6 and 7.
The signals to be transmitted, arising from a source (not shown) are applied at 8 and, if necessary, are frequency or amplitude modulated. In particular, if the input signals are video signals, they are used just as they are, in the baseband without modulation; on the contrary, if the signals are of an other nature, for .;
~5;72~3 example audio signals which usually accompany -the video signals, -they are conveniently modulated in order to be superimposed on the video signals.
The resulting signa:L con-trols then the input voltage of a current generator assembly 10, followed by a symmetrical transformer 56, preferably with a mag-netic core. After -transmission by wires 6 and 7 of the line, the signals flow through a second symme-trical transformer 102, also with a magne-tic core, and through a differential amplifier 12, followed generally by a filter 13 in order to permit only the passage of the required signals. The differential amplifier 12 elimi-nates in particular the asymmetrical voltages on wires 6 and 7 due to outside interferences, while filter 13 separates the elementary signals thus transmitted. At the output of the filter, the signals are possibly de-modulated in a demodulator circuit 14, then amplified at 15 prior to reaching the device output 16.
Transformers 56 and 102 are directly part of the transmission line formed by leads 6 and 7. Prefer-ably, these transformers include windings coiled by means of twin-wire leads. Advantageously, the windings of the transformers are even made by the wires 6 and 7 of the line. In the drawing of Fig. 2, reference numerals 17 and 18 on the one hand, 19 and 20 on the other hand, show schematically the connections of the line with the transmitting and recei~ving assemblies, the black dots in Fig. 2 showing in a schematic way the winding direction of the transformers.
Fig. 3 shows in more de-tail the embodiment of a transmitter assembly 4, used in the device according to the invention.
As seen in Fig. 3, one inputs at 21 and 22 on wires 6 and 7 of the line the signals to be trans-mitted, supplied by transmitter 4 in the following manner: two current generators 23 and 24, having i72~3 identical characteristics, are connected to the trans-mission line at poin-ts 21 and 22. The current gener-ators are designed to output a current that is linearly proportional to the input signal (Erom adder 31) inde~
penden-t of the loading of the line and without disturb-ing the symmetry of the system. I-t is noted tha-t the current generators contemplated for use in the present invention are commonplace and a number of designs would perform satisfactorily. The terminals of generators 23 and 24 are saturated by a loading impedance unit 25 in series wi-th a capacitor 25a, the capacitor providing for the separation of the alternating and direct compo-nents of the current.
Impedance unit 25 is equal to the character-istic impedance of the line. It is preferably formed by means of two equal resistors, respectively 95 and 96, having each a resistance value equal to half the characteristic impedance of the line, the node between the two resistors being connected to ground through a capacitor 97. The o-ther terminals of generators 23 and 24 are respectively connected to a positive power supply via a current limiter 26 and to a negative power supply. A current detector 27 can be provided in the circuit of the generators.
The current limiter 26 protects the gener-ators, notably in the accidental event of a short cir-cuit between the transmission wires 6 and 7 or between ground and either lead.
On the o-ther hand, the two generators 24 and 23 are fed by the signal from the adder 31 and its inverse, respectively, by means of inverter 28. Of course, the number of inputs can be different from two, whereby the transmitter can receive at the input as many signals as necessary on as many parallel channels.
In the example shown, it is assumed that a video signal and an audio signal are inputted at 29 and ., ,,J
ii72~3 30, respectlvely. The video signal is fil-tered at 32 and the audio signal can be amplified by a variable gain amplifier 33 and modulated at 34 before the two signals are added at 31. The two signals are frequency separated in the -transmi-t-ter passband, the transmi-tter of the present inventlon generally processlng slgnals between 50 Hz and 30 MHz.
The mounting of transmitter 4 wlth its cur-ren-t generators 23 and 24 in turn mounted in series with lmpedance 25 which is equal to the llne character-lstlc impedance thus allows passlng from an asymme-trlc operation at the lnput at 29 and 30 for -the signals, to a perfectly symmetrical operatlon at the output of the generators, notably at 21 and 22 where sald signals are introduced on -the transmlsslon line. At the ou-tput of the generators, the resulting signal transmitted on the line, whlch ls equal to the dlfference of -the voltages on the wlres of sald llne, represents the relatlve value of the slgnals at the transmltter lnput.
The symmetrical operation thus provided on the line two leads avoids therefore an lnterference radlatlon during transmission as well as -the effect of interference fields at the reception.
The circuit of Flgure 3 also contains means for receivlng signals, for example remote control signals, propagating on the same transmission line but in an opposite direction to those transmitted by trans-mitter 4. The means includes a differential amplifier 172 mounted between points 21 and 22, followed by a 3Q passband fil-ter 173, a demodulator 174, and an ampli-fier 175. The signals outputted at 176 can be used to control the selection of signals to be introduced into the transmitter, corresponding in this example to points 29 and 30.
In Fig. 4 is shown a receiving assembly of the device, with an impedance uni-t 55 and a capacitor ~, ~
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7~3 55a iden-ti.cal to impedance uni-t 25 and capaci-tor 25a of the transmit-ter assembly. Two curren-t generators 35 and 36, whose power feed is ins-tead coupled to the lines 6 and 7 at 37 and 38, respectively, are si-tuated to produce the proper vol-tage at points 40 and 41.
Impedance unit 55 and the two genera-tors 35 and 36 in series are mounted in parallel be-tween terminals 37 and 38 of a diode bridge ll, the o-ther two terminals of which being connected at 17 and 18 to the two wires 27 of the transmission line. As already indicated, said diode bridge is used for avoiding the disadvan-tage of a possible polarity inversion during assembly, so as to receive on generators 35 and 36 the signals delivered by the transmitter generators 23 and 24.
Generators 35 and 36 are separated by a volt-age limiter of the Zener diode 39 type. At the termi-nals 40 and 41 of said diode is collected the feeding voltage for the various circuits of the receiver assem-bly.
To terminals 37 and 38 of generators 35 and 36 are thus connected a differential amplifier 42. At the output of said amplifier is -two output channels.
One includes a passband filter 43 and a demodulator 44 the output 45 of which supplies to any user the audio signal injected at 30 at the input of transmitter 4 (Fig. 3). On the other channel, the signal flows through a rejection filter 46 eliminating the audio subcarrier and supplying, after having passed through an amplifier 47, on an output 48, the video signal such as i-t had been injected to the transmitter at 29. The output 48 can be a standard output for video signals, at 75 ohms.
The present device allows transmit-ting in the reverse direction signals received by receiver 5 con-cerning other informat.ion, for example remote controlsignals. In this case, one can advantageously foresee that said signals, received at 168 from an appropriate source (not shown), firs-t modulated in a modulating circui-t 169, control thereaf-ter the voltage of a cur-rent generator 170 opera-ting symmetrically, mounted in parallel with the receiver assembly 5 between terminals 37 and 38.
By analogy with Fig. 3, it should be s-tressed that it is possible to mount at the output of the differential amplifier 42 as many channels as required for allowing the reception of a correspondiny number of signals representing distinct information, whereby said signals can be modulated or not, as the case may be.
Likewise, it is obvious that it is also possible to di-rectly connect to output 48 any type of apparatus using said signals, for example a television set having a video input or a monitor.
Fig. 5 shows the means used in the present device for completing the balancing of the voltages set in operation. In Fig. 5, the elements which were es-sential in previous Figs. 2, 3 and 4 have been shownagain, by indicating, from the positive power feed of the transmitter up to the negative power feed, the evaluation of -the voltages adopted, -the values of said voltages being of course purely indicative. For the very low frequency components or the continuous compo-nent of the voltages on the generators, the latter can behave as resistors. On each generator is shown, mounted in parallel, a resistor R and an inductance coil L symbolizing together the circuits used.
3a Therefore, one will find in the same order, from top to bottom, corresponding to the decreasing voltages from the positive to the negative, current limiter 26, generator 23, terminal 19, transmission wire 6, terminal 17, one of the active diodes of diode bridge 11, terminal 37, genera-tor 35, terminal 40, Zener diode 39, terminal 41, generator 36, terminal 38, the other ac-tive diode of diode bridge 11, terminal 18, -transmission wire 7, -terminal 20 and genera-tor 24.
The dashes passing by terminals 17, 18, 19, 20 bound symbolically transmit-ter 4 and receiver 5.
The syrnmetrical transformers with magnetic cores have been omitted here and are assumed to be in-cluded in the transmission line. Also, the impedance units 25 and 55 have also not been shown.
The assembly shown forms a voltage divider, here between +16 V and -8 V, the two wires 6 and 7 being respec-tively raised to +11.5 V and -3.5 V repre-senting a potential difference of +4.5 V across each of generators 23 and 24. The power feed outputs 40 and 41 of receiver 5 are respectively raised to +7.5 V and to ground, a poten-tial difference of +4 V across gener-ators 35 and 36 and of +7.5 V across the Zener diode 39.
If one wishes ground 41 of receiver 5 and ground 49 of transmitter 4 to be at the same potential, 2Q equal to 0 V, it is therefore necessary that the vari-ous resistors provide for the balance between terminals 50-49 and 50-41 on the one hand, and 49-51 and 41-51 on the o-ther hand. This voltage balance is accomplished by the proportionality of the equivalent resistors and of complementary resistors 52 and 53, the latter being associated to a capacitor 54 providing for the ground-ing of the power feed for the alternating signals.
Thus is provided a signal transmission device of very simple design, allowing sending said signals over a long distance in a wide frequency band, from a transmitter receiving said signals towards a receiver to the use. Said signals can be of any nature and can in particular be video signals in the baseband, most often associated with a modulated audio signal without prejudice to other signals being added to the previous ones. Said signals control the voltage of current . ~
,572~3 - ~.6 -genera-tors which, on the transmit-ter side, energize the transmission line, said genera-tors opera-ting in opposi--tion and being connected to an impedance unit equal to the line characteristic impedance. Said same signals, at the reception, feed the receiver with con-tinuous current and res-tore the power feed by means of two symmetrical current generators, connected to a Zener diode, the signals at the output passing -through a differential ampliEier in which they are treated for restoring without interference or rnodification the input signals. On the other hand, the device allows superimposing to the transmission -thus carried ou-t -the sending of signals in the reverse direction, for exam-ple of the remote control -type conveniently modulated, said signals being transmitted in the receiver by an independent current generator, delivering in parallel on the line.
Of course, i-t is obvious that the invention is not limited to the examples especially described and 2~ shown and that on the contrary it encompasses all the variants thereof. In particular, the line leads can be cylindrical and parallel, or flat and placed side by side. Preferably, said wires are kept parallel to one another by an insulating material, allows a uniform characteristic impedance along the line.
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Background of -the Invention Many signal and/or data transmission devices between two distant points separated by a de-termined distance are already known in the art. In particular, many systems using connec-tions by coaxial cables or transmission lines called "buses" are known. However, with these standard systems, and when the task is to transmit video signals, it is generally necessary that said signals are frequency or amplitude modulated and that they do not remain in the baseband if one wishes to avoid a quick degradation of said signals, which is all the more important as the diameter of the coaxial cables used is smaller. With cables of large diameter, the degradation of the signal is less but the instal-lation is costly and above all less convenient. The problem is forming passages in the walls through which the large diameter cables are to pass to provide con-nections with the equipment at said locations. Forcables of smaller diameter, a frequency or amplitude modulation of the signals is always necessary, thereby making necessary the use of a modulator and then of a demodulator, introducing some distortion and limi-tations. Moreover, some of said systems designed forlong range transmission of signals from the output of a tape recorder or those which are to be applied to the input of a television set of a known type, and using the demodula-tor present in the standard -television sets, are incompatible with the use of simple visuali-2~3 zation moni-tors.
The present invention is a device allowing the -transmission of at least one signal, such as but no-t limited to a video signal, maintained in the base-band without modulation. The device is reliable,simple -to produce and allows transmitting a signal without disturbing it, wi-thout this signal disturbing the environmen-t, or without being itself disturbed by said environment. The device also has a wide pass-band, excellent linearity and a signal/noise ratioremaining satisfac-tory across said band.
More particularly, the invention is directed to a transmission device which allows transferring signals corresponding to information of any nature and of the type which can be found in many industrial as well as domestic applications. Thus, in the case of hotels and communities for example, the presen-t device allows advantageously communication from a given cen-tral station, or more generally between several sta-tions. The present device can transmit various tele-phonic, radio, or television messages, information relating to security, the supervision and the eventual control of inlets and outlets, the change of codes or door locks, and the usage of some sexvices, wake-up calls, etc. In such applications, it is obvious that when the account of information that can be transmitted by leads of small section becomes more important, the multiplication of unaesthetic and bulky cables and the disadvantages due to setting them in place increases in proportion. The limitation to the twin-wire line of the invention, each having a diameter which can be no-tably less than 1 mm, allows easy passage of the lines underneath washboards, be-tween floor planks, underneath doors, and underneath carpets. This is a great advan-tage particularly in homes or hotels.
On the other hand, in the video and trans-, .., ~
. . .~, ~ ., I I, mission of television images field, i-t is known that said images come more and more frequently from various sources, notably tape recorders, cameras, converters of signals transmitted by coaxial cables or optic fiber beams, video disc readers, and television sets. The problem is establishing communication upon request from each of said sources at will with other receivers or moni-tors at the disposal of the users. Outside even the hotel or community field, for exarnple a simple domestic usage, one can easily imagine the possibility of establishing inside the same home a transmission assembly, possibly connected with an audiophonic assem-bly, allowing a remote -transmission from one room -to the other of the television images accompanied by sound signals and also remotely controlling the sources of said signals.
The present invention is therefore directed to a multi-input transmission device for conveying signals, such as video signals, but possibly of an 2Q other nature, which can be transmitted according to the standards of any system (SECAM, PAL, NTSC, D2 MAC PAQUET ...) and are from any appropriate source (a receiver for a ratio transmitter, a receiver antenna for transmissions from satellites, cables, etc. The device avoids the use of bulky and costly transmission coaxial cables that are liable to introduce interfer-ence in the various signals transmitted, especially if the cables are of a great length.
Transmission systems using two leads of small diameter are certainly already known. Thus, FR-A-2 584 555 refers to a wide band signal transmission device in a network, possibly of video-communication with a star-shaped structure, where the video infor-mation can be remotely transmitted to a plurality of distinct receiving sets. In such systems, the signals to be transmitted are adapted in an input equipment and e~
transmitted -to an output equipment via a balanced and symmetrical twin-wire line -through a switching matrix including M lines and N columns interconnected, the matrix being associated with an address memory allowing selection of the chosen switching address. Finally in said systems, the transmitted signals are filtered in the input equipment so as to separate the low and high frequency components, each of which being the object of a transmission on the twin-wire line according to a different mode. Regarding the high frequency compo-nent of the signal, it is sent in a differen-tial mode through a transformer, the two components going, in the outpu-t equipment, through a summation device for reconstituting the signal. Such a device is costly, complex and risks introducing signal distortion wi-th a poor signal/noise ratio, above all if the frequency band is made relatively wider.
With respect to the prior art thus shown, the present invention has the advantage of a very simple device, allowing -transmitting in optimal conditlons any signals received at its input, whatever the standard used. With the present device it is not necessary to separate the high and low frequency signals in the signal spectrum, instead said signal can be immediately remotely transmitted in its whole extent by the two leads of the line equipped with symmetrical trans-formers, due to an appropriate adaptation and a balanc-ing of the line avoiding the radiation of said line.
To this effect, the signal transmission de-3Q vice, transmitting signals between at least one trans-mitter assembly and at least one receiver assembly by means of a twin-wire connecting line of small diameter, equipped at each end with a symmetrical transformer and powered by at least one current generator, is charac-terized in that the current generator outputs symmetri-cally to the line and is controlled by the signals to ~, r;
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be transmitted. Said signals generally have a fre-quency between 50 Hz and 30 MHz and the line is balanc-ed at each end by an impedance equal to its character-istic impedance.
Advantageously, the two identical wires are not shielded and each have a diameter less than or equal to 1 mm, it being understood here tha-t -the in-vention has its essential advan-tages in -the use of leads of small diameter but larger diameter wires can be used. Moreover, although it is obvious that the wires oE the line have preferentially a circular cross-section, they could also be flat, notably in the shape of tapes placed on an insula-ting support or imbedded in said support, without departing from the scope of the invention.
Preferably also, the symmetrical transformers fitting out each end of the two wire lines have mag-netic core with each winding mounted in series with one of the wires of the line. According to a particu-2Q lar embodiment, the windings of the symmetrical trans-formers are themselves made of the line wires. These transformers strongly reduce line noise without damping the high frequency components of the transmitted sig-nals.
According to another feature of the inven-tion, each transmitting assembly includes two current generators, one controlled by a signal and the other by the inverse of -that same signal and delivering sym-metrically on one and the other of the line wires, said 3Q generators being mounted in series with a matching impedance unit having a value which is equal to the line characteristic impedance. Preferably, the imped-ance unit in series with the generators includes resis-tors and a capacitor adapted to separate the continuous component from the signals to be transmitted. More-over, the matching impedance unit is advantageously . ~ .
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7~3 formed by means of two equal impedance uni-ts moun-ted in series and with -the node be-tween -the two units connect-ed to the ground via a capaci-tor. Likewise, in each receiver assembly, the matching impedance unit of the line is mounted in parallel on said line and is as such made of -two equal impedance units mounted in series with a medium point connected to the ground.
According to another advantageous feature of the invention, each receiver assembly includes two current genera-tors supplying the power supply current to said assembly. Moreover, and according to another feature, the receiver assembly includes a complementary current generator, operating symmetrically, with its voltage controlled by modulated signals, distinct frorn those controlling the generators of the transmitter assembly, whereby said signals can be in par-ticular remote controlled signals circulating on the twin-wire line in a direction reverse to that of the signals re-ceived from the transmitter.
Brief Description of Drawings Other characteristics of a signal trans-mission device according to the invention will become apparent from the following description of an embodi-ment, given as an indicative and non limiting example, with reference to the accompanying drawings wherein:
- Fig. 1 is a systematic diagram showing on the ordinate the maximum voltage of a signal trans-mitted as a function of the length of the transmission wires in any line, plotted in abscissa.
- Fig. 2 is a schematic block diagram of the transmission device according to the invention.
- Fig. 3 shows in greater detail the device transmitter assembly.
- Fig. ~ shows also in greater detail the device receiver assembly.
., ~ ~ ' .
7'~3 - Fig. 5 is a block diagram of the device which allows to better understand the implementation of the means which also provide, accordiny to the inven-tion, the voltage balancing oE the device.
- Eig. 6 is a diagram of the twin-wire trans-mission line.
Detailed Description of the Invention Generally, it is known from -theory and ex-perience that in a signal transmission installation using a twin-wire line, it is possible to considerably reduce the radiation created by the assembly of the two wires by reducing the dissymmetry of the operation durirlg transmission. The device according to the in-vention basically takes advantage of this observation.
In Fig. 1 is shown on curve 1 the maximum voltage of a signal transmitted as a function of the length of the transmission wires for a glven maximum radiation limit. Curve 1 which is na-turally decreasing shows in practice irregularities if the transmission is not symmetrical, the wires behaving as an antenna. On said same Fig. 1 is shown by curve 2 the influence of the voltage created by the interference due -to the outer electrical field on the line, also as a function of the wire length.
One can thus establish that this influence increases substantially linearly when -the transmission wire path is rectilinear. On the contrary~ if said wires follow complex paths, which is generally the case in applications of interest where the signals have to be transmitted between two distant locations by the line following an appropriate path which conceals it as best as possible, curve 2 becomes complex since its slope depends on very many factors and particularly on the frequency of the outer field and on the shape of said field. One infers therefrom that for better z~
-transmission it is advantageous -that the intersection point 3 of curves 1 and 2 be as remote as possible from the abscissa axis for a more efficien-t transmission.
This condition is substantially met when there is a symmetry in -the transmission line. In fact, the greater the symmetry the higher curve 1 is on the diagram of Fig. 1 and the smaller -the slope of curve 2, which permits a greater possible length of transmission without interference. Moreover, -the use of such a sym-me-try in the line avoids the need for shielding for the conducting wires.
Therefore, the present device takes advantage of the hereabove observations. To this eEfect, it in-cludes substantially a transmission line with two wires of small diameter, of the order of 1 mm or less, con-necting a transmitter assembly to a receiver assembly.
Said wires are cylindrical and parallel, maintained in position by an appropriate insulating material. The transmitter assembly includes a variable number of in-2Q puts, adapted to be connected to various signal sourcesand a receiver assembly having the same or a different number of outputs which can be connected to user appa-ratus, receiving and exploiting signals incoming from the transmitter and others arriving on the line. The twin-wire transmission line and the respective trans-mitter and receiver assemblies form the basis of the device. The transmitter and receiver can be mounted symmetrically or be each transmitting and receiving.
Moreover, one can foresee on the line the possible need 3Q for intermediate transmitters or receivers so that a signal can be received and then retransmitted in order to ensure its integrity along the line to other re-ceivers. Likewise, complementary signals which are superimposed on the line with those that are already transmitted by said line can be in-troduced at each intermediate receiver, without interfering with said t~
,. .
57~3 signals and wi-th the operation of the line.
According to the inven-tion, at each end of the transmission line is connected, through symmetrical transformers current generators having their character-istics and control mode chosen according to the inven-tion for ensuring a perfect symmetrical balancing of -the whole assembly. In particular, each current gener-ator is designed in such manner as -to allow sending a signal and/or a current on the line or to take a signal lQ from said line, without modifying the loading impedance value of said line. In the transmitting assembly, the current generators have their voltage controlled in a symmetrical way from the signals to be transmitted. In the receiver assembly, the generators are connected to the ends of -the -transmission wires, preferably and as will be seen hereafter via a diode bridge in order to avoid polarity errors when connecting the wires.
In a most general way, the device is there-fore designed for providing a permanent balancing of the line as regards the direct voltages, particularly by avoiding any possibility of shorts to ground. More-over, at the level of each transmitter and/or receiver, a particular balancing with respect to the line sym-metry is also ensured by means of an impedance unit mounted in series with the current generators, said impedance unit is in turn parallel to the transmission wires in order to form, each time, a circuit where the alternating voltages involved are balanced.
In Fig. 2, the line transmission wires are 3Q respectively designated by reference numerals 6 and 7.
The signals to be transmitted, arising from a source (not shown) are applied at 8 and, if necessary, are frequency or amplitude modulated. In particular, if the input signals are video signals, they are used just as they are, in the baseband without modulation; on the contrary, if the signals are of an other nature, for .;
~5;72~3 example audio signals which usually accompany -the video signals, -they are conveniently modulated in order to be superimposed on the video signals.
The resulting signa:L con-trols then the input voltage of a current generator assembly 10, followed by a symmetrical transformer 56, preferably with a mag-netic core. After -transmission by wires 6 and 7 of the line, the signals flow through a second symme-trical transformer 102, also with a magne-tic core, and through a differential amplifier 12, followed generally by a filter 13 in order to permit only the passage of the required signals. The differential amplifier 12 elimi-nates in particular the asymmetrical voltages on wires 6 and 7 due to outside interferences, while filter 13 separates the elementary signals thus transmitted. At the output of the filter, the signals are possibly de-modulated in a demodulator circuit 14, then amplified at 15 prior to reaching the device output 16.
Transformers 56 and 102 are directly part of the transmission line formed by leads 6 and 7. Prefer-ably, these transformers include windings coiled by means of twin-wire leads. Advantageously, the windings of the transformers are even made by the wires 6 and 7 of the line. In the drawing of Fig. 2, reference numerals 17 and 18 on the one hand, 19 and 20 on the other hand, show schematically the connections of the line with the transmitting and recei~ving assemblies, the black dots in Fig. 2 showing in a schematic way the winding direction of the transformers.
Fig. 3 shows in more de-tail the embodiment of a transmitter assembly 4, used in the device according to the invention.
As seen in Fig. 3, one inputs at 21 and 22 on wires 6 and 7 of the line the signals to be trans-mitted, supplied by transmitter 4 in the following manner: two current generators 23 and 24, having i72~3 identical characteristics, are connected to the trans-mission line at poin-ts 21 and 22. The current gener-ators are designed to output a current that is linearly proportional to the input signal (Erom adder 31) inde~
penden-t of the loading of the line and without disturb-ing the symmetry of the system. I-t is noted tha-t the current generators contemplated for use in the present invention are commonplace and a number of designs would perform satisfactorily. The terminals of generators 23 and 24 are saturated by a loading impedance unit 25 in series wi-th a capacitor 25a, the capacitor providing for the separation of the alternating and direct compo-nents of the current.
Impedance unit 25 is equal to the character-istic impedance of the line. It is preferably formed by means of two equal resistors, respectively 95 and 96, having each a resistance value equal to half the characteristic impedance of the line, the node between the two resistors being connected to ground through a capacitor 97. The o-ther terminals of generators 23 and 24 are respectively connected to a positive power supply via a current limiter 26 and to a negative power supply. A current detector 27 can be provided in the circuit of the generators.
The current limiter 26 protects the gener-ators, notably in the accidental event of a short cir-cuit between the transmission wires 6 and 7 or between ground and either lead.
On the o-ther hand, the two generators 24 and 23 are fed by the signal from the adder 31 and its inverse, respectively, by means of inverter 28. Of course, the number of inputs can be different from two, whereby the transmitter can receive at the input as many signals as necessary on as many parallel channels.
In the example shown, it is assumed that a video signal and an audio signal are inputted at 29 and ., ,,J
ii72~3 30, respectlvely. The video signal is fil-tered at 32 and the audio signal can be amplified by a variable gain amplifier 33 and modulated at 34 before the two signals are added at 31. The two signals are frequency separated in the -transmi-t-ter passband, the transmi-tter of the present inventlon generally processlng slgnals between 50 Hz and 30 MHz.
The mounting of transmitter 4 wlth its cur-ren-t generators 23 and 24 in turn mounted in series with lmpedance 25 which is equal to the llne character-lstlc impedance thus allows passlng from an asymme-trlc operation at the lnput at 29 and 30 for -the signals, to a perfectly symmetrical operatlon at the output of the generators, notably at 21 and 22 where sald signals are introduced on -the transmlsslon line. At the ou-tput of the generators, the resulting signal transmitted on the line, whlch ls equal to the dlfference of -the voltages on the wlres of sald llne, represents the relatlve value of the slgnals at the transmltter lnput.
The symmetrical operation thus provided on the line two leads avoids therefore an lnterference radlatlon during transmission as well as -the effect of interference fields at the reception.
The circuit of Flgure 3 also contains means for receivlng signals, for example remote control signals, propagating on the same transmission line but in an opposite direction to those transmitted by trans-mitter 4. The means includes a differential amplifier 172 mounted between points 21 and 22, followed by a 3Q passband fil-ter 173, a demodulator 174, and an ampli-fier 175. The signals outputted at 176 can be used to control the selection of signals to be introduced into the transmitter, corresponding in this example to points 29 and 30.
In Fig. 4 is shown a receiving assembly of the device, with an impedance uni-t 55 and a capacitor ~, ~
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7~3 55a iden-ti.cal to impedance uni-t 25 and capaci-tor 25a of the transmit-ter assembly. Two curren-t generators 35 and 36, whose power feed is ins-tead coupled to the lines 6 and 7 at 37 and 38, respectively, are si-tuated to produce the proper vol-tage at points 40 and 41.
Impedance unit 55 and the two genera-tors 35 and 36 in series are mounted in parallel be-tween terminals 37 and 38 of a diode bridge ll, the o-ther two terminals of which being connected at 17 and 18 to the two wires 27 of the transmission line. As already indicated, said diode bridge is used for avoiding the disadvan-tage of a possible polarity inversion during assembly, so as to receive on generators 35 and 36 the signals delivered by the transmitter generators 23 and 24.
Generators 35 and 36 are separated by a volt-age limiter of the Zener diode 39 type. At the termi-nals 40 and 41 of said diode is collected the feeding voltage for the various circuits of the receiver assem-bly.
To terminals 37 and 38 of generators 35 and 36 are thus connected a differential amplifier 42. At the output of said amplifier is -two output channels.
One includes a passband filter 43 and a demodulator 44 the output 45 of which supplies to any user the audio signal injected at 30 at the input of transmitter 4 (Fig. 3). On the other channel, the signal flows through a rejection filter 46 eliminating the audio subcarrier and supplying, after having passed through an amplifier 47, on an output 48, the video signal such as i-t had been injected to the transmitter at 29. The output 48 can be a standard output for video signals, at 75 ohms.
The present device allows transmit-ting in the reverse direction signals received by receiver 5 con-cerning other informat.ion, for example remote controlsignals. In this case, one can advantageously foresee that said signals, received at 168 from an appropriate source (not shown), firs-t modulated in a modulating circui-t 169, control thereaf-ter the voltage of a cur-rent generator 170 opera-ting symmetrically, mounted in parallel with the receiver assembly 5 between terminals 37 and 38.
By analogy with Fig. 3, it should be s-tressed that it is possible to mount at the output of the differential amplifier 42 as many channels as required for allowing the reception of a correspondiny number of signals representing distinct information, whereby said signals can be modulated or not, as the case may be.
Likewise, it is obvious that it is also possible to di-rectly connect to output 48 any type of apparatus using said signals, for example a television set having a video input or a monitor.
Fig. 5 shows the means used in the present device for completing the balancing of the voltages set in operation. In Fig. 5, the elements which were es-sential in previous Figs. 2, 3 and 4 have been shownagain, by indicating, from the positive power feed of the transmitter up to the negative power feed, the evaluation of -the voltages adopted, -the values of said voltages being of course purely indicative. For the very low frequency components or the continuous compo-nent of the voltages on the generators, the latter can behave as resistors. On each generator is shown, mounted in parallel, a resistor R and an inductance coil L symbolizing together the circuits used.
3a Therefore, one will find in the same order, from top to bottom, corresponding to the decreasing voltages from the positive to the negative, current limiter 26, generator 23, terminal 19, transmission wire 6, terminal 17, one of the active diodes of diode bridge 11, terminal 37, genera-tor 35, terminal 40, Zener diode 39, terminal 41, generator 36, terminal 38, the other ac-tive diode of diode bridge 11, terminal 18, -transmission wire 7, -terminal 20 and genera-tor 24.
The dashes passing by terminals 17, 18, 19, 20 bound symbolically transmit-ter 4 and receiver 5.
The syrnmetrical transformers with magnetic cores have been omitted here and are assumed to be in-cluded in the transmission line. Also, the impedance units 25 and 55 have also not been shown.
The assembly shown forms a voltage divider, here between +16 V and -8 V, the two wires 6 and 7 being respec-tively raised to +11.5 V and -3.5 V repre-senting a potential difference of +4.5 V across each of generators 23 and 24. The power feed outputs 40 and 41 of receiver 5 are respectively raised to +7.5 V and to ground, a poten-tial difference of +4 V across gener-ators 35 and 36 and of +7.5 V across the Zener diode 39.
If one wishes ground 41 of receiver 5 and ground 49 of transmitter 4 to be at the same potential, 2Q equal to 0 V, it is therefore necessary that the vari-ous resistors provide for the balance between terminals 50-49 and 50-41 on the one hand, and 49-51 and 41-51 on the o-ther hand. This voltage balance is accomplished by the proportionality of the equivalent resistors and of complementary resistors 52 and 53, the latter being associated to a capacitor 54 providing for the ground-ing of the power feed for the alternating signals.
Thus is provided a signal transmission device of very simple design, allowing sending said signals over a long distance in a wide frequency band, from a transmitter receiving said signals towards a receiver to the use. Said signals can be of any nature and can in particular be video signals in the baseband, most often associated with a modulated audio signal without prejudice to other signals being added to the previous ones. Said signals control the voltage of current . ~
,572~3 - ~.6 -genera-tors which, on the transmit-ter side, energize the transmission line, said genera-tors opera-ting in opposi--tion and being connected to an impedance unit equal to the line characteristic impedance. Said same signals, at the reception, feed the receiver with con-tinuous current and res-tore the power feed by means of two symmetrical current generators, connected to a Zener diode, the signals at the output passing -through a differential ampliEier in which they are treated for restoring without interference or rnodification the input signals. On the other hand, the device allows superimposing to the transmission -thus carried ou-t -the sending of signals in the reverse direction, for exam-ple of the remote control -type conveniently modulated, said signals being transmitted in the receiver by an independent current generator, delivering in parallel on the line.
Of course, i-t is obvious that the invention is not limited to the examples especially described and 2~ shown and that on the contrary it encompasses all the variants thereof. In particular, the line leads can be cylindrical and parallel, or flat and placed side by side. Preferably, said wires are kept parallel to one another by an insulating material, allows a uniform characteristic impedance along the line.
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Claims (18)
1. A transmission device for signals, in-cluding video signals, comprising:
at least one transmitter assembly including first and second current generators mounted in series with a matching impedance;
at least one receiver assembly including a diode bridge;
a twin-wire line connecting said transmitting and receiving assemblies;
a symmetrical transformer having a magnetic core mounted on each end of said line, the windings of said transformer made from twin-wire cable;
said first generator being driven by a signal to be transmitted and delivers a current symmetrically into one wire of said line;
said second generator being driven by the in-verse of said signal to be transmitted and delivers a current symmetrically into the other wire of said line;
wherein said line is balanced at each end by an impedance of a value equal to the characteristic impedance of said line, and said matching impedance is of a value equal to the characteristic impedance of said line, and said signals are in a frequency range of 50 Hz to 30 MHz.
at least one transmitter assembly including first and second current generators mounted in series with a matching impedance;
at least one receiver assembly including a diode bridge;
a twin-wire line connecting said transmitting and receiving assemblies;
a symmetrical transformer having a magnetic core mounted on each end of said line, the windings of said transformer made from twin-wire cable;
said first generator being driven by a signal to be transmitted and delivers a current symmetrically into one wire of said line;
said second generator being driven by the in-verse of said signal to be transmitted and delivers a current symmetrically into the other wire of said line;
wherein said line is balanced at each end by an impedance of a value equal to the characteristic impedance of said line, and said matching impedance is of a value equal to the characteristic impedance of said line, and said signals are in a frequency range of 50 Hz to 30 MHz.
2. A device according to Claim 1, wherein the two wires are identical and have a diameter which is less than or at most equal to 1 mm.
3. A device according to Claim 1, wherein the twin-wire cable forming the windings of the symmet-rical transformers is made from the wires of the line.
4. A device according to any one of Claims 1 to 3, wherein the transmitter assembly and the receiver assembly are respectively a receiver and a transmitter.
5. A device according to Claim 1, wherein the matching impedance, in series with the generators, includes resistors and a capacitor adapted for sepa-rating the continuous component of the signals to be transmitted.
6. A device according to Claim 1, wherein the matching impedance of the line is made of two equal impedance units mounted in series, a node, where said impedance units are joined, being connected to ground through a capacitor.
7. A device according to Claim 1, wherein in each receiver assembly, the line matching impedance is mounted in parallel on said line and is made of two equal impedance units mounted in series, a node, where said impedance units are joined, being connected to ground through a capacitor.
8. A device according to Claim 1, wherein the receiver assembly includes two current generators supplying a feeding current for said receiver assembly.
9. A device according to Claim 8, wherein the receiver assembly includes a complementary current generator operating symmetrically having its voltage controlled by modulated signals distinct from those controlling generators of the transmitter assembly.
10. A device according to Claim 9, wherein the modulated signals which control the complementary generator are remote control signals.
11. A device according to Claim 1, wherein the transmitter assembly includes a limiter for the feeding current of generators.
12. A device according to Claim 11, wherein the current limiter is connected to a positive power feed terminal of one of generators, a detector being connected to its negative power feed terminal.
13. A device according to Claim 1, wherein the signals to be transmitted which control the current generators of transmitter result from the superimposi-tion of first signals and of second signals, previously modulated and possibly amplified.
14. A device according to Claim 1, wherein the signals transmitted to the receiver assembly via line pass through a differential amplifier and are separated by filtering.
15. A device according to Claim 8, wherein a voltage limiter is mounted between the two current gen-erators of the receiver assembly.
16. A device according to Claim 15, wherein the voltage limiter is a Zener diode.
17. A device according to Claim 8, wherein the current generators are equivalent to a resistor with respect to the current continuous component.
18. A device according to Claim 1, wherein the line wires can be cylindrical and are kept parallel by means of a common covering made of an insulating ma-terial.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8701338 | 1987-02-04 | ||
| FR8701338A FR2610464A1 (en) | 1987-02-04 | 1987-02-04 | METHOD AND DEVICES FOR TRANSMITTING SIGNALS BY SMALL SECTION CONDUCTORS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1295728C true CA1295728C (en) | 1992-02-11 |
Family
ID=9347575
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000557783A Expired - Fee Related CA1295728C (en) | 1987-02-04 | 1988-02-01 | Transmission device, notably video signals |
Country Status (19)
| Country | Link |
|---|---|
| US (1) | US5089886A (en) |
| EP (2) | EP0300016B1 (en) |
| JP (1) | JPH01502070A (en) |
| KR (1) | KR890700973A (en) |
| AT (1) | ATE81238T1 (en) |
| AU (1) | AU1246388A (en) |
| BR (1) | BR8805087A (en) |
| CA (1) | CA1295728C (en) |
| DE (1) | DE3874993T2 (en) |
| DK (1) | DK551988A (en) |
| ES (1) | ES2035930T3 (en) |
| FI (1) | FI89435C (en) |
| FR (1) | FR2610464A1 (en) |
| GR (1) | GR3006710T3 (en) |
| IE (1) | IE880305L (en) |
| MC (1) | MC1976A1 (en) |
| NO (1) | NO884386L (en) |
| PT (1) | PT86673B (en) |
| WO (1) | WO1988005979A1 (en) |
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| US20080229378A1 (en) * | 2004-11-09 | 2008-09-18 | Leaf Audio Pty. Ltd. | System and Method of Distributing Audio and Video Signals |
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| FR2932338A1 (en) * | 2008-06-10 | 2009-12-11 | Commissariat Energie Atomique | SYSTEM FOR TRANSMITTING AN ELECTRICAL SIGNAL, PARTICULARLY FREQUENTIAL, AND DEVICE FOR MEASURING RADIATION EQUIPPED WITH SUCH A SYSTEM |
| US8897215B2 (en) | 2009-02-08 | 2014-11-25 | Corning Optical Communications Wireless Ltd | Communication system using cables carrying ethernet signals |
| JP5685858B2 (en) * | 2010-08-27 | 2015-03-18 | ソニー株式会社 | Camera device, camera system, and camera control method |
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| US9184960B1 (en) | 2014-09-25 | 2015-11-10 | Corning Optical Communications Wireless Ltd | Frequency shifting a communications signal(s) in a multi-frequency distributed antenna system (DAS) to avoid or reduce frequency interference |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1814453A (en) * | 1930-07-21 | 1931-07-14 | Osborne Ralph Willoughby | Protective device for communication apparatus used with communication lines subjected to extraneous voltage |
| US3290653A (en) * | 1963-01-10 | 1966-12-06 | Control Data Corp | Single ended to double ended to single ended communication system |
| GB1234186A (en) * | 1967-09-05 | 1971-06-03 | ||
| IT1063336B (en) * | 1975-03-17 | 1985-02-11 | Sits Soc It Telecom Siemens | CABLE DISTRIBUTION SYSTEM FOR LARGE BAND SIGNALS |
| US4054910A (en) * | 1976-02-26 | 1977-10-18 | Tel-E-Tel, Inc. | Communication system for the transmission of closed circuit television over an ordinary pair of wires |
| DE2633066C2 (en) * | 1976-07-22 | 1978-06-08 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Device for the transmission of push-pull signals over a two-wire line in duplex mode |
| JPS5717242A (en) * | 1980-07-07 | 1982-01-28 | Yokogawa Hokushin Electric Corp | Data line |
| FR2518858A1 (en) * | 1981-12-23 | 1983-06-24 | Jeumont Schneider | DEVICE FOR TRANSMITTING SIGNALS ON A LINE ALSO PROVIDING A CONTINUOUS VOLTAGE SUPPLY |
| FR2584555B1 (en) * | 1985-07-08 | 1988-08-05 | Duret Christian | END EQUIPMENT FOR BROADBAND TRANSMISSION |
| DE3525519A1 (en) * | 1985-07-17 | 1987-02-05 | Messerschmitt Boelkow Blohm | TRANSFER SYSTEM |
| US4751607A (en) * | 1986-08-11 | 1988-06-14 | American Telephone And Telegraph Company | Communication line transient protection |
-
1987
- 1987-02-04 FR FR8701338A patent/FR2610464A1/en not_active Withdrawn
-
1988
- 1988-01-27 MC MC88FR8800046D patent/MC1976A1/en unknown
- 1988-01-27 DE DE8888901421T patent/DE3874993T2/en not_active Expired - Fee Related
- 1988-01-27 WO PCT/FR1988/000046 patent/WO1988005979A1/en active IP Right Grant
- 1988-01-27 JP JP63501474A patent/JPH01502070A/en active Pending
- 1988-01-27 BR BR8805087A patent/BR8805087A/en unknown
- 1988-01-27 AT AT88901421T patent/ATE81238T1/en not_active IP Right Cessation
- 1988-01-27 EP EP88901421A patent/EP0300016B1/en not_active Expired - Lifetime
- 1988-01-27 AU AU12463/88A patent/AU1246388A/en not_active Abandoned
- 1988-02-01 CA CA000557783A patent/CA1295728C/en not_active Expired - Fee Related
- 1988-02-01 PT PT86673A patent/PT86673B/en not_active IP Right Cessation
- 1988-02-02 ES ES198888400243T patent/ES2035930T3/en not_active Expired - Lifetime
- 1988-02-02 EP EP88400243A patent/EP0281440B1/en not_active Expired - Lifetime
- 1988-02-04 IE IE880305A patent/IE880305L/en unknown
- 1988-10-03 NO NO884386A patent/NO884386L/en unknown
- 1988-10-03 DK DK551988A patent/DK551988A/en not_active Application Discontinuation
- 1988-10-03 FI FI884549A patent/FI89435C/en not_active IP Right Cessation
- 1988-10-04 KR KR1019880701236A patent/KR890700973A/en not_active Application Discontinuation
-
1990
- 1990-05-24 US US07/527,720 patent/US5089886A/en not_active Expired - Fee Related
-
1992
- 1992-12-30 GR GR920403246T patent/GR3006710T3/el unknown
Also Published As
| Publication number | Publication date |
|---|---|
| NO884386D0 (en) | 1988-10-03 |
| PT86673B (en) | 1994-08-31 |
| FI884549A0 (en) | 1988-10-03 |
| FI89435B (en) | 1993-06-15 |
| DE3874993T2 (en) | 1993-04-29 |
| IE880305L (en) | 1988-08-04 |
| PT86673A (en) | 1989-02-28 |
| KR890700973A (en) | 1989-04-28 |
| DE3874993D1 (en) | 1992-11-05 |
| DK551988D0 (en) | 1988-10-03 |
| GR3006710T3 (en) | 1993-06-30 |
| EP0281440A1 (en) | 1988-09-07 |
| FR2610464A1 (en) | 1988-08-05 |
| BR8805087A (en) | 1989-08-15 |
| NO884386L (en) | 1988-10-03 |
| ES2035930T3 (en) | 1993-05-01 |
| WO1988005979A1 (en) | 1988-08-11 |
| JPH01502070A (en) | 1989-07-13 |
| ATE81238T1 (en) | 1992-10-15 |
| EP0300016A1 (en) | 1989-01-25 |
| MC1976A1 (en) | 1989-10-26 |
| US5089886A (en) | 1992-02-18 |
| EP0300016B1 (en) | 1992-09-30 |
| DK551988A (en) | 1988-10-03 |
| FI884549A (en) | 1988-10-03 |
| EP0281440B1 (en) | 1992-09-30 |
| AU1246388A (en) | 1988-08-24 |
| FI89435C (en) | 1993-09-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |