DE1816746A1 - Method and device for cable transmission of electrical signals between a television camera and its control unit - Google Patents

Description

French patent application No. 13 3 820 (Seine)

The invention relates to a method for transmission over Coaxial cable of electrical signals between a television camera and the control unit that mainly controls it, and the device for performing this method. This method makes it possible in particular to have a large amount of information in the direction of the control unit of the camera and the camera by means of a very small number on ladders, even by means of only one conductor, without reducing the quality of this information.

In a television image pickup device using one or more image pickup cameras, numerous signals are required different frequency and bandwidth in the two directions from the control unit to the camera and vice versa be transmitted. The control unit can be located in a studio or in a report trolley, for example.

In fact, the control unit has to send a signal for energy supply, synchronization signals, to each camera that is dependent on it for line and raster scanning of the image pickup tube and control signals of the various electrical and optical Parameters of the camera, such as the screen voltage and the current of the cathode ray, the aperture setting and the setting of the lens, the gain of the video amplifier ... transmitted. The camera must go to the control unit from which it is controlled, the video signal it generates is transmitted.

Furthermore, in almost all such systems, an interphone must work between the control units and the image recording camera can.

In various cases it must be possible to transmit further signals. These are e.g. an antenna display that the operator aa-seigt the periods during which his image acquisition used effectively, or an auxiliary video signal, which is transmitted from the control unit to the camera, where it creates an image on the electronic display device and the The operator enables him to regulate certain assemblies himself.

This information to be transmitted is for color television recordings much more numerous and extensive.

In general, the connection between the control unit and the camera is made by a complex cable, which is practical consists of as many conductors as there are different signals to be transmitted. The number of these conductors can be used for black and white shots 30 and 100 for color images.

The disadvantages inherent in these cables are numerous and the more severe the longer the connection to be made is the case, for example, with reportage cameras

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is. The greater the number of conductors _s is actually the greater the price and the weight of the cable center. Furthermore, the connection cable camera includes a large number of taps and thus increases the risk of breakdowns »

Were to avoid these wax parts in particular at a reportage su, a method for forming a connection between the control unit and the camera was used _s at the Hertz'sehe compounds used "In this case, the camera comprises a high-frequency ~ transceiver device" This overall 3? Ät is powered by a battery "Even if the lack of a cable makes such a device seem cheap," it still has serious disadvantages. The unit camera = battery is bulky and heavy "The independence of the camera depends on that of the battery _s which is all the more limited as the image recording tube j for example an orthicon = picture tube _{9 has} a high energy consumption ο the propagation conditions limit the possibilities due to the necessarily high frequency for the carrier of the transceiver? Use of such a device «The operator has to be practically in the immediate visual range of the reporting vehicle»

The invention has the object of providing a method and apparatus for performing this method of the initially named kind _s allows an interference-free transmission of control signals in a small number of connecting lines between the control unit and camera in both the black and white and in color television "by the ist = In the case of the method proposed here, this invention is above all ": solved by the fact that the invention _f ~ ernäü; the various signals or signal groups to be transmitted are converted in terms of frequency, regardless of their transmission direction, in such a way that

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any signal or group of signals in that from the coaxial cable The transmitted frequency band occupies a certain frequency range that is determined by, through the other signals or Signal groups occupied frequency ranges is separated by a frequency interval that is large enough to Avoid crosstalk · By using this technique, the number of conductors making up the cable will be increased decreased. A single conductor with a large pass bandwidth, such as a coaxial cable, can be used. This method of transmission of several signals between a control unit and a television camera by means of frequency Implementation of the various signals can and can be used for both black-and-white and color television can be used by combining the signals in various forms within the frequency band passed through the transmission cable is transmitted.

One form of the method of the invention for black and white television consists in the fact that the energy supply of the camera is transmitted as DC voltage that continues to be from The video signal output by the camera is transmitted in its normal frequency band, as well as the various signals supplied by the control unit for controlling the parameters of the camera and that by the control unit Low-frequency interphone signal "Give" transmitted to the camera are narrow bandwidth time-division multiplexed signals that modulate a first carrier, its frequency is chosen such that between the frequency range occupied by the multiplex signal and that of the Video signal occupied frequency range lying frequency interval is sufficient, and that finally that of The interphone signal "coming" transmitted from the camera to the control unit modulates a second carrier whose frequency

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is chosen such that between that of the Interfon-> signal "coming" occupied frequency range and occupied by the multiplex signal modulating the first carrier Frequency interval lying within the frequency range is sufficient is.

The inventive device for carrying out this method for Schwärζweiß-Fernsehen is that the connection between the control unit and camera is formed by only one coaxial cable, that also at the end of the coaxial cable to which the control unit is connected, a feed circuit which is connected to the coaxial cable outputs a DC voltage, and a DC / DC converter is provided on the camera side, a video amplifier circuit which transmits the signal supplied by the image pickup tube of the camera to the coaxial cable, and a video amplifier circuit is provided on the control circuit side, which further processes the received signal that furthermore for processing the low-frequency signal group transmitted from the control unit to the camera and the interphone signal "give" a multiplex circuit is provided on the one hand on the side of the control unit, which includes a counter which is shifted in time enen pulses a division circuit feeds, which carries out a division of the different signals to be transmitted and whose output supplies the time-shifted division pulses to a coding and modulator circuit, which forms the multiplex signal and thus modulates the first carrier, and on the other hand on the side of the camera a multiplex the pulses of the transmitted modulated signal declaratory detector circuit and a circuit arrangement is provided which sets the corresponding him modulated pulse to a signal associated with each decoding circuit, and that finally for processing the interphone _signal ti ii _{Koinmen on the side}

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the camera has a modulator circuit modulating the second carrier with the signal to be transmitted, and on the side of the Control unit, an amplifier circuit that determines and amplifies the received signal is provided.

An advantageous embodiment of the device according to the invention consists in the fact that the feed signal used to supply power to the camera is high voltage and low current having.

Another advantageous embodiment of the invention The device is that an inductance-capacitance circuit for decoupling the feed signal and of the video signal is provided in the circuits of the camera and the control unit.

Another advantageous embodiment of the invention Device consists in that the inductance-capacitance circuit has a frequency-independent impedance which is equal to the characteristic impedance of the coaxial cable.

Another advantageous embodiment of the invention The device consists in that the video amplifier connected between the image pick-up tube and the coaxial cable has such a frequency response that it over-amplifies the low-frequency components of the video signal so that the the lowering of these components brought about by the inductance is compensated.

Another advantageous embodiment of the invention The device is that an auxiliary circuit is provided in the camera circuits, which the video signal adds an extra pulse during the line suppression periods, and that in the video amplifier on the side of the

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Control unit a separating circuit is provided which separates the additional pulses, their phase comparison with the line synchronization pulses the control unit results in a low-frequency error signal which is used to control the line scanning is transmitted to the camera through one channel of the time-division multiplexed signal.

Another advantageous embodiment of the invention The device consists in that the division frequency of the multiplex signal is a multiple of the raster frequency and that the raster synchronization signal to the camera in one Channel of the multiplex signal is transmitted by switching modulation of the pulses of this channel in such a way that each the presence or absence of a raster pulse is indicated during the instant of denomination.

Another advantageous embodiment of the invention Apparatus consists in that the division frequency is a multiple of the line frequency.

Another advantageous embodiment of the device according to the invention is that the multiplex frequency or the frequency of the pulses of the multiplex signal is a multiple of the line frequency.

Another advantageous embodiment of the device according to the invention consists in the fact that a multiplex synchronization signal with a frequency equal to the denomination frequency to the MuHjjplexsignal on the control unit side is added so as to enable the selection of the pulses according to the channel to which they belong.

Another advantageous embodiment of the invention Device consists in that the / multiplex signal

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processing circuit on the side of the camera at the output the detector circuit which detects the multiplex pulse on the one hand, a control circuit that sends a switching signal to a counter with each passage of a pulse, and on the other hand a circuit which extracts the multiplex sync signal which is the zeroing of the Counter controls whose output signals are successively AND gates open, at the input of which the pulses are applied that are emitted by the detector circuit, and their output with each belonging to one channel of the multiplex signals Decoders are connected, which supply the camera with the control signals transmitted in these channels.

Another advantageous embodiment of the invention The device consists in that the modulators of the pulses of the multiplex signal through the denominations of the to transmitted control signals is a width modulation.

Another advantageous embodiment of the device according to the invention is that the multiplex synchronization signal consists of an over-amplitude of a certain width of all pulses of the same channel.

Another advantageous embodiment of the device according to the invention is that the various circuits to transform the signals to be transmitted and to process the transmitted signals via filters to the Coaxial cables are connected.

Another form of the method according to the invention is that the output from the camera and to the control unit transmitted video signal modulates a carrier, while the time-division multiplexed signal either without frequency conversion or by modulating a carrier with a

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Frequency lower than that of the video signal modulated carrier is transmitted to the camera.

Further features and advantages achieved by them emerge from the description of the drawing in which, for example selected embodiments of the device according to the invention and a diagram explaining the method according to the invention are shown; Show it:

Fig. 1 shows the schematic representation of the frequency distribution of various between a camera and a camera controlling control unit for black and white television signals to be transmitted,

2 shows a simplified overview diagram of a black and white television used embodiment of the device according to the invention,

3 shows a simplified scheme for decoupling the feed signal from the video signal in the control unit and the camera.

In the method according to the invention, a certain number of known transmission technologies combined in a new form and this combination on the transmission of electrical Signals are applied between a television recording camera and the control unit that controls it.

In general terms, this method consists in frequency distribution of the various signals to be transmitted make in the form that each signal or each signal group occupies a precisely defined frequency range, the differs enough from the neighboring areas occupied by other signals that crosstalk between these signals is avoided. The totality

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this range is chosen so that the multiplex signal obtained has a bandwidth that is less than the pass bandwidth of a broadband conductor such as a coaxial cable, In this way, all signals to be transmitted are transmitted in both directions via a single cable.

In certain cases of color photos or photos with special effects, For example, involving numerous film assemblies, it may be advantageous to use multiple conductors and to transmit a signal multiplexed in the manner according to the invention on each. Also in these cases is this transmission method with the multiplex converted signal is advantageous because it enables the number of conductors to reduce the transmission cable considerably.

This method is described below with reference to FIG. 1 in an application in black and white television. In the Fig. 1 is an example selected Ibrm of the frequency distribution of the various signals to be transmitted. For the sake of simplicity, no frequency scale has been used in FIG. 1 specified.

The signals to be transmitted from the control unit to the camera exist in the usual black and white recording devices from an energy supply signal and a certain number of previously enumerated control signals, among which the interphone signal from the control unit or the interphone signal "Give" is located. The essential characteristic of these control signals is that they have a narrow bandwidth. In fact, a bandwidth of around 3 KHz is sufficient for the interphone signal. Those controlling the parameters of the camera Signals are either low-frequency (raster synchronization signal) or practically adaptable to control signals. Iir. the latter Case, depending on the reference signals of the control

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unit or from regulations that it must carry out, change the signals of the camera for the supply or regulation of certain Parameters are supplied. These control signals, which are actually correction signals, change slowly and need to be only a small bandwidth for your transmission.

The signals to be transmitted from the camera to the control unit are the useful video signal, for example the frequency band 50 Hz includes 5 MHz in the 625 line standard, and the interphone signal "Coming", the bandwidth of which is 3 KHz.

All of these signals are frequency-converted and distributed within the frequency band that belongs to the single coaxial cable is transmitted. The following signals are generated on the coaxial cable in the manner shown in FIG transfer:

the feed signal 1 is transmitted as direct voltage,

the useful video signal 2 is without frequency conversion in the Transfer baseband,

the low-frequency control signals are time-multiplexed on a first carrier F ₁ , which they modulate with the sidebands 3 and 4,

the interphone signal "coming" is transmitted on a second carrier F _{2 which} it modulates.

The values of the carrier F. and F ₂ are selected in such a way that they have a sufficient frequency spacing between the frequency ranges occupied by the various signals. These values can be, for example, F ₁ = 20 MHz and F- 30 MFIz.

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This preferred form of frequency distribution has numerous advantages.

The transmission of the supply energy to the camera as direct voltage is to be preferred to an alternating voltage supply. Indeed this avoids spreading the frequency spectrum. This makes it easier to convert the other signals in terms of frequency. It also eliminates the presence of extensive Elements such as transformers and filter circuits, which would be necessary if the supply were to be carried out by alternating voltage (e.g. 50 Hz), avoided in the camera. The elements that operate in the camera's DC / DC converter in terms of AC current will be operated at high frequencies and are therefore not extensive.

The transmission of the useful video signal emitted by the camera in its normal frequency range (for example 50 Hz - 5 or 6 MHz) lets the heavier weight of the camera through avoid the circuits that would be necessary for frequency conversion to a carrier.

The transmission of the control signals in the form of a time-division multiplexed signal that modulates the first carrier F ,, makes it possible to to transmit a large amount of different information in a sufficiently narrow frequency band. In the in In the example shown in FIG. 1, the modulation of the carrier by the multiplex signal is an amplitude modulation with two Sidebands. However, another type of modulation (single sideband modulation) can also be used. The multiplex signal corresponds to the usual signals of the pulse-multiplexing technique. It is made up of a series of impulses that on a frequency called the "denomination frequency" which contain information related to the successive

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Denominations belong to the same signal. Between two pulses of a signal belonging to two following denominations the pulses that belong to the denominations of the other signal to be transmitted are inserted. The repetition frequency of the pulses that make up the multiplex signal and each represent one of the signals to be transmitted in the course of a denomination period, is hereinafter referred to as "multiplex frequency" designated. The multiplex frequency is a multiple of the division frequency. The proportionality factor is the same the number of different signals to be transmitted.

For example, if there are ten signals to be transmitted, the denomination period comprises ten "channels", each having a duration equal to a period of the "multiplex frequency" and each of which contains information associated with a denomination of one of the ten signals. In the following Beschrxebenen embodiment of the device according to the invention the multiplex frequency is advantageously a common multiple of the line and screen frequencies.

Such a multiplexing by pulses is due to the low bandwidth of each of the control signals to be transmitted easy to do. In fact, as has already been stated, the "give" inter-hair dryer signal has a bandwidth of about 3 KIIz. The other signals are either low-frequency or can be adjusted to the slowly changing control signals. The bandwidth of the cell synchronization signal is, for example "about 1 KIIz. The denomination frequency does not have to be very high to meet the usual denomination requirements suffice.

In Fig. 2 is an embodiment of the invention Device for black and white television shown schematically. In this embodiment a single coaxial cable ensures 6 the electrical connection between a recording

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camera and the control unit that controls it. In Fig. 2, only the parts are shown in block form, which for the Description of the device according to the invention required are. The parts shown on the right in FIG. 2 are for the camera and those shown on the left are for the control unit intended. The upper part of FIG. 2 bounded by the cable 6 represents the circuits which are used in both Directions to be transmitted different. Process signals and consider them compliant with the signals as they are for the transmission method are defined. The lower part of Fig. 2 shows the circuits which the so transmitted Process information.

The energy supply of the camera, which is transmitted by direct voltage, is connected to the cable 6 on the side of the control unit applied by a feed circuit 7, which may be stabilized in the usual way. To the Joule effect To limit the losses caused in the cable, this feed to the cable is carried out by a high DC voltage transmitted with low amperage. On the camera side, a DC voltage converter 8 reduces this voltage, provides the power through the voltages Vl, Vn, which are necessary for the supply of the various organs of the camera and stabilize these tensions if necessary.

The useful video signal supplied by the image pickup tube 9 of the camera, which the cable 6 via video amplifier 10 feeds, is, as already stated, transmitted in its normal frequency band without frequency conversion. In the example considered here with a 625 line standard, the band of frequencies to be transmitted extends from about 50 Hz to 5 or 6 MHz.

Under these conditions, it is necessary to have both the circuits of the supply signal and the circuits of the video signal

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to be decoupled from each other in the control unit as well as in the camera. Such decoupling usually becomes easy formed by a circuit that is looped into the feed circuit Inductor and one looped into the video circuit Has capacitor. The inductance must have a sufficiently high value for effective decoupling even at the lowest frequencies of the video signal 50 Hz - to ensure. In the present case it is one of those simple arrangement with two components is not sufficient. In effect is the relative change in the frequency of the video signal between the extreme frequencies of its band - 50 Hz, 5 or 6 MHz - significant and the coaxial cable is in this The entire band cannot be adapted if certain measures are not taken, in particular to reduce the effect of the interference capacitance to compensate for the inductance that occurs at the highest frequencies of the band.

^{In order} to avoid this mismatch, the circuit of the inductance L and the capacitor C is completed in a known form according to the scheme of FIG. 3 by two resistors R of the same value and an inductance 1 which satisfies the equation - ^ - = R, where ρ is the interference capacitance of the inductance L. The special feature of this circuit is that its impedance from point A or point B is purely ohmic and practically independent of frequency. The load on the cable 6 is thus constant over the entire frequency band. In order for the cable to be matched for all frequencies in this band, it is sufficient if this load is the same characteristic impedance of the cable.

The _{useful video signal supplied by the camera's pick-up tube} 9 is applied to the cable via a video amplifier 10 and is processed by a video amplifier 11 on the control unit side.

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An auxiliary circuit of the camera included in the amplifier circuit 10 of FIG. 2 completes that of the tube output Nutζ video signal by displaying this during the Periods of line suppression adds pulses whose repetition frequency is the line frequency. On the website In the control unit, the amplifier 11 comprises a circuit which generates this pulse 12 at line frequency from the useful video signal 13 separates. The phase of the pulses 12 thus extracted from the transmitted video signal becomes with phase of the line synchronization pulses of the control unit in a phase discriminator, not shown, compared to the one Emits an error signal that is sent to the camera via one of the "multiplex channels" is transmitted.

In addition, the video signal output by the pickup tube 9 is given a pre-emphasis in the amplifier 10, which consists in the fact that the low-frequency components are over-amplified compared to the high-frequency components. Through this it is made possible to have an inductance in the decoupling circuit less high value to use. In fact, this is due to the less effective decoupling in the case of the low-frequency ones Components of the video signal caused attenuation is compensated by their preamplification.

The time division multiplexing described briefly above of the low frequency signals leads to a certain number of special characteristics of those described for black and white television Embodiment.

The division frequency of the multiplexed signal, which has already been defined not to include only the frequency in which the low-frequency signals to be transmitted are fragmented, but also the repetition frequency of the multiplexed signal of the pulses of a "channel", i.

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of the same low-frequency signal is on the one hand dependent of the usual laws of denomination and, on the other hand, of the raster synchronization depending on the type of transmission elected.

In an advantageous embodiment, this is raster synchronization signal at raster frequency on one of the "channels" of the multiplex signal from the control unit to the camera, which then this signal is used directly to control their raster scan. So that this raster synchronization signal is appropriately reproduced in its "channel", it is necessary in this case that the denomination frequency is a multiple the screen frequency, i.e. a multiple of 50 Hz. In the case of black and white television with a 625 line standard this frequency is chosen to be 12.5 KHz, for example. This frequency - a multiple of 50 Hz - is completely sufficient in order to divide the low-frequency signals appropriately, and enables a condition of the multiplex frequency to be explained below to meet.

One embodiment of this type would be to provide a Use denomination frequency that is a multiple of the Line frequency is ._ In this case, the ^ beginning of the Raster pulses transmitted over a channel are always combined with a pulse with a line frequency. To rectify enforcement, these pulses must be delayed by a half line for one of two rasters. This embodiment is therefore much more difficult to manufacture than those described above and complicates the, in particular, in the Camera necessary parts.

Which is advantageously fulfilled by the multiplex frequency The condition is that this is a multiple of the line frequency is. Indeed, the pulses of the multiplex signal, in this case simply starting from the usual ones, are stable

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Receive oscillators that deliver the line synchronization pulses in the circuits of the control unit. This will the use of an additional stable and therefore not easy to manufacture oscillator is avoided. This condition becomes in the case described here a multiplex signal with 10 "channels" fulfilled by choosing a denomination frequency of 12.5 KIIz. In fact, the frequency is multiplexed therefore equal to 10 χ 12.5 KHz = 125 KHz = 8 χ 15.-6 2-5, i.e. that Eight times the line frequency.

In an advantageous embodiment, for example, there is the multiplex signal from a sequence of pulses, the repetition frequency of which is 125 KHz and those with a frequency of 12.5 KHz cyclically for the denomination of one of the ten transmitted low-frequency Contain information related to signals.

This information is carried, for example, by the pulses in the form of a width modulation of the pulse Leading edge remains fixed and its width depends on the value of the denomination of the signal it represents. That Synchronization signal, which theoretically could be transmitted directly on its "channel", is also through a width modulation of the pulses transmitted at multiplex frequency. In this case it is a switching modulation, which indicates the presence or absence of raster pulses at the instant of the denomination. This modulation is necessary in the event that the denomination frequency is a multiple of the screen frequency and that the device making the selection the pulses of each "channel" hits, the leading edges of the pulses of the multiplex signal taken into account.

So that each multiplex signal is used appropriately by the camera, a synchronization signal is assigned to it, its Frequency is equal to the denomination frequency. This synchronization signal consists, for example, of a

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Upper amplitude certain width on one of the "channels" _s, for example, the multiplexed signal is transmitted to the first ".... . ■ ;.

The circuits j which the multiplex signal on the side of the Form control unit and process it on the side of the camera, are shown schematically in Fig. 2 and in the following for the case of a multiplex signal with 10 "channels" described «

In the circuit of the control unit, a counter IM- fed by pulses Ij received by a pilot oscillator at a frequency of, for example, 125 KHz, supplies ten time-shifted pulses at 10 different outputs Sl, Si, Sn. A circuit element 15, which is fed on the one hand by the low-frequency signals BFl, BFi, BFn to be transmitted and on the other hand by the shifted pulses supplied by the counter 14 _{, divides the signals BFl 9} BFi, BFn in an arrangement of conventional analog gates and supplies a sequence of denomination pulses in the form of a series which follow one another at the multiplex frequency. The output of this circuit element 15 is connected to a further circuit arrangement 16 which, based on the shifted division pulses, supplies the, for example, width-modulated coded pulses which comprise the synchronization signal of the multiplexing which forms the multiplexed signal. Furthermore, this circuit arrangement 16, which is controlled by an oscillator 17, the frequency of which is the first carrier frequency FpI (for example 20 MHz), develops the transmitted modulated signal (FIG. 1, signal 3, U).

In the circuit arrangement of the camera, the transmitted signal is processed by a circuit, which is an amplifier

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with automatic gain control which is suitable for the '. Received signal guaranteed regardless of the length of the cable 6, a constant level. This circuit, represented by block 18 in FIG. 2, also includes a demodulator which demodulates the received signal and extracts the multiplexed signal therefrom. The output of this amplifier-detector circuit 18 is connected to circuitry which ensures the selection of the pulses of the multiplex signal according to the "channel" to which they belong and therefore to the signal they represent and the pulses of each "channel" a corresponding decoder Dl, Di, Dn applies, which supplies the camera with the various control signals BFl, BFi, BFn.

This pulse selection circuit comprises two switching elements 19 and 20, each of which is for forward switching and zeroing a counter 21 - for example a ring counter - to which its three outputs are located.

The first switching element 19 supplies a pulse which controls the upward switching of the counter 21 each time it detects the leading edge of a pulse of the multiplex signal, ie the transition from one channel to the next. The second circuit element 20 controls the zero setting of the counter 21 each time it detects the multiplex synchronization signal - for example with excessive amplitude.

The output at the outputs of COUNTER 21 signals equal in number to the channels - in the example described, ten - open one after each of the ten AND gates 1, i, n 'whose other input receives the output from the detector 18 multiplex signal and whose output at the input of one of the decoders Dl, Di, Dn.

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The circuits that do the processing of the interphone signal Ensuring "coming" consist on the camera side of an element 22 which the second carrier Fp2 (for example 30 MHz) modulated with the interphone signal P to be transmitted, and on the side of the control unit from an element 23, which is an amplifier with automatic gain control and a detector which demodulates the interphone signal P.

In order to avoid crosstalk between the different signals transmitted in this way on the same cable 6, are Filters are assigned to the various circuits that feed the signals to the cable or take signals from the cable. It should be noted that the frequencies of the multiplex signal are chosen proportional to the line and screen frequencies, if there is interference between this multiplex signal and the useful video signal. Which is in the picture The resulting errors are fixed and are therefore not very visible.

There are numerous forms of the transfer method and apparatus of the invention for implementation this procedure is conceivable. Some of these shapes are described below.

One form of the method according to the invention consists in distributing the various signals or signal groups in a frequency distribution within the passband of the coaxial cable, that of that shown in FIG Distribution is different. In particular, the video signal 2 (Fig. 1) and the group of time-division multiplexed Signals 3, 4 are swapped.

Another form is to transmit additional signals. If, for example, it is necessary to transmit several low-frequency signals from the camera to the control unit.

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carry, these signals can be combined into a second time-division multiplexed signal, for example, the carrier F λ modulates. Various other signals can still transmit - for example a second video signal that modulates a different carrier (e.g. 50 MHz).

When the low frequency signals transmitted by the multiplex signal are very numerous and these signals or only some of these signals have very narrow bandwidths Another form is to convert the "channels" of the multiplex signal or just some of these "channels" into "sub-channels" subdivide. Each "channel" subdivided in this way then transmits its own multiplex signal, which is several of the represents low-frequency signals to be transmitted.

In the case of color television, the connection between the control unit and the camera can be established by a single cable, by using, for example, the following signal distribution: The luminance signal becomes like the video signal in the for the example described in black and white television. The chrominance signal, which comprises two or three components, is transmitted by multiplexing these components on a special carrier. The various control signals the three or four image pick-up tubes are time-division multiplexed by a signal that is another special Modulated carrier, transmitted on subdivided "channels".

In certain cases it may be necessary to use the cable To protect transmitted signals against interference caused by strong interference fields. This protection can be formed by using, for example, a coaxial cable with double shielding that the interference attenuates considerably, or by using a shielded pair of coaxial cables. In the latter case it will

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Transmit the signal on one of the two cables. The second cable is used to establish the reference potential. That between The signal running on the two cables is practically not affected by a disturbance.

The transfer method according to the invention and the device for performing this method make it possible in Numerous forms of electrical connections between an image capture camera and its control unit by means of a single cable »that carries a large number of signals in both directions. The circuitry that enables such a connection are easy to manufacture. The circuit arrangements required in the camera are poor Weight and small footprint. The pulse multiplexing circuit is particularly adapted for manufacture in integrated circuits.

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Claims (1)

Patent claims: Method for the transmission of electrical signals over coaxial cables between a television camera and the control unit that mainly controls it, characterized in that the various signals or signal groups to be transmitted are converted in terms of frequency, regardless of their direction of transmission, in such a way that each signal or each signal group in that of the coaxial cable The transmitted frequency band occupies a certain frequency range, which is separated from the frequency ranges occupied by the other signals or signal groups by a frequency interval which is sufficiently large to allow crosstalk to be avoided. 2. The method according to claim 1 for black and white television, characterized in that the energy supply of the camera as DC voltage (1) is transmitted that the video signal output by the camera continues in its normal Frequency band (2) is transmitted, that also the various from the control unit to control the parameters The signals supplied to the camera and the interphone signal "Give" transmitted from the control unit to the camera are low-frequency are narrow bandwidth time-division multiplexed signals modulating a first carrier (F 1), - 7 - 1 7 5 - 2 ' whose frequency is selected in such a way that the frequency range between the frequency range occupied by the multiplex signal (3, and the frequency interval lying within the frequency range occupied by the video signal is sufficient, and that finally the interphone signal "coming" transmitted from the camera to the control unit a second carrier (F 2) modulated, the frequency of which is selected in such a way that the "coming" between the interphone signals Frequency range (5) and the frequency range occupied by the multiplex signal modulating the first carrier (3, 4 ·) lying frequency interval is sufficient is. 3. Apparatus for performing the method according to claim 2, characterized in that the connection between the control unit and the camera is formed by only one coaxial cable (6), and that a feed circuit (7) is also provided at the end of the coaxial cable to which the control unit is connected ), which outputs a direct voltage to the coaxial cable, and a direct current converter (8) is provided on the side of the camera, and a video amplifier circuit (10), which the signal supplied by the image pick-up tube (9) of the camera, is also provided on the side of the camera on the coaxial cable (6), and on the side of the control circuit a video amplifier circuit (11) is provided, which further processes the received signal that continues to process the low-frequency signal group transmitted from the control unit to the camera and the interphone signal "give" on the one hand Side of the control unit a multiplex circuit is provided which ^{comprises a counter (I 1} +), which in z Eitally shifted pulses feeds a division circuit (15) which divides the various signals to be transmitted (BF ^ ₅ BF ^, EF) and whose output the temporal 909829/1175 ΘΑΟ ORiQiNAt jf - shifted division pulses to a coding and modulator circuit (16), which forms the multiplex signal therefrom and thus modulates the first carrier (F, ), and on the other hand, on the side of the T.arnera, a detects the multiplexed pulses of the transmitted modulated signal Detector circuit (18) and sine Sc ": - ..; .- 3 arrangement (19, 20, 21, ET", ET _n ., ET) provided ·: -.-: -: t, die "1 to a Del · or be _{,. "." ung (D 1} , D., D) belonging to each signal the corresponding mod., values I:, ds, ■ and that finally for processing: es Inx? _. rucnsignals "Coming" (P) on the side of the camera a ue ,. second carrier (F _? ) with the signal-regulating modulator circuit (22) to be transmitted and an amplifier circuit (23) which detects and amplifies the received signal is provided on the side of the control unit. 4. Apparatus according to claim 3, characterized in that Gaß the feed signal used to supply power to the camera has high voltage and low amperage. 5. Apparatus according to claim 3 or 4, characterized in that an inductance-capacitance circuit for decoupling of the feed signal and the video signal is provided in the circuits of the camera and the control unit. 6. Apparatus according to claim 5, characterized in that the inductance-capacitance circuit is frequency-independent Has impedance which is equal to the characteristic impedance of the coaxial cable (6). 7. Apparatus according to claim 5 or 6, characterized in that between the image pickup tube (9) and coaxial cable (6) switched video amplifier (10) has such a frequency response that it removes the low-frequency components - 4 - 909829/1175 $ AD OBiQiNAt of the video signal is over-amplified _{5 in} such a way that the lowering of these components caused by the inductance is compensated " ο Device according to one of Claims 3 to 7 _3, characterized in that an auxiliary circuit is provided in the camera circuits which feeds the video signal during the number suppression period. an additional pulse adds 3 and that in a video amplifier (11) on the side of the control unit a disconnect switch .; -ung is provided:., which separates the additional pulses, the phase comparison with the line synchronization pulse. cc ι control unit err ^ t a low-frequency error signal. which is transmitted to control the line scanning on the Kair.er <ü through a channel of the time-division multiplexed signals. J "device according to one of claims 3 to 0 ₂ in that the denomination frequency of the multiplex = signal is a multiple of the screen frequency and that the raster synchronization signal WI5 transmitted to the camera in EIASM channel of the multiplex signal by a sound modulation of the pulses of this channel so? _S d that the presence or absence of a raster pulse during the instant of the denomination is indicated. 1oo device according to claim 9 ₉ characterized in that the denomination _s actual frequency is a multiple of the line frequency Il ο apparatus of claim 3 _9, characterized in that _s the multiplex frequency, or the frequency of the pulses of Kultiplexsignals is a multiple of the line frequency « S. \ 12. Device according to one of claims 3 to 11 _s thereby; characterized in that a multiplex synchronization signal 8329/1 1? BADOfHGiNAL with a frequency equal to the division frequency, the multiplex signal on the side of the control unit in this way it is added that the selection of the pulses is made possible according to the channel j to which they belong. 13. The apparatus according to claim 12, referring back to claim 9, characterized in that the multiplex signal processing Circuit on the side of the camera at the output of the detector circuit which detects the multiplex pulses (18) on the one hand a control circuit (19) which sends a switching signal to a Counter (21) supplies, and on the other hand comprises a circuit (20) which extracts the multiplex synchronization signal, which controls the zero setting of the counter, whose output signals open one after the other AND gates, to whose Input the pulses are present, which are emitted by the detector circuit (18), and their output with each decoders belonging to a channel of the multiplex signals (D) are connected, which supply the camera with the control signals transmitted in these channels. 14. Device according to one of claims 3 to 13, characterized characterized in that the modulation of the pulses of the multiplex signal is a width modulation due to the denominations of the control signals to be transmitted. 15. Apparatus according to claim 14, characterized in that the multiplex synchronization signal from an upper amplitude there is a certain width of all pulses of the same channel, 16. The method according to claim 2, characterized in that the output from the camera and transmitted to the control unit Video signal modulates a carrier, while the time-division multiplexed signal either without frequency conversion "" "" "909829/1 175 Jo ■■ or by modulating a carrier at a frequency lower than that modulated with the video signal The carrier is transmitted to the camera. 17. Device according to one of claims 3 to 15, characterized characterized in that the various circuits for reshaping the to be transmitted. Signals and for processing of the transmitted signals are connected to the coaxial cable via filters. 9 0 9829/117 5