DE2934227C2 - Arrangement for tuning a television receiver to the output channel of an RF converter in a recording and / or reproducing device - Google Patents

Description

The invention relates to an arrangement for tuning a television receiver to the output channel an HF converter in a recording and / or playback device according to the generic term of the ! 0 saying 1.

In the description, the term "RF converter" denotes a circuit that has a RF carrier wave generated and which modulates the RF carrier wave with a video signal to a to form modulated oscillation that corresponds to one of the channels in a television receiver.

Electronic tuning devices are used more and more frequently for television receivers Tuning devices are designed in such a way that when channels are preset, a variable resistance is set so that it changes a tuning voltage changeable and that it thereby on the desired channel frequency is set.

In the UHF areas, the radio and television channels in particular are spread over one arranged in a wide frequency range. Therefore, the frequency scale marks are generally not accurate enough that they can be used for the channel preset mentioned above. In practice, a Operator viewing the reproduced image on a screen of a television receiver (abbreviated to »TV« receiver), carry out a channel coincidence setting, which means that a channel is preset is performed.

On the other hand, is in an apparatus for magnetically recording video signals on a magnetic tape and / or reproducing such signals from such a tape (hereinafter abbreviated as "VTR") High frequency converter included that converts a signal reproduced from a magnetic tape into a signal converts that can be received by the television receiver. Hence e:> When connecting the VTR to the television receiver, it is necessary to make a preset so that a certain empty Channel that is not used to receive broadcast channels for the television receiver, exactly with the Output frequency (the channel) of the RF converter in the VTR.

Numerous television receivers have recently come on the market that use electronic voting devices which act so that either when an empty channel has been selected or when none Signal from the transmitting station, no white noise on the screen of the television receiver

and that the entire screen therefore remains black and does not close at any point starts to glow. If such a television receiver is connected to the VTR, it is not works so that it plays a tape, then the screen of the television receiver will not light up because that The output signal of the high-frequency converter is only a non-modulated carrier signal. Therefore can a certain free channel of such a television receiver is not on the output channel (frequency) of the High frequency converter can be set.

As a result, the pre-setting of the output channel of the RF converter in the VTR was previously set to one empty channel made to a prerecorded

Tape in the VTR by using the resulting reproduced Signa! the television receiver and by then adjusting the variable resistance of the empty channel above until a clear picture was reproduced on the television receiver from the tape.

This known method has various disadvantages, which are that it is necessary reproduce a prerecorded tape so that rather difficult preparatory work is required, and that if a prerecorded tape is not available, the RF converter output channel cannot be differentiated or discriminated, so that a default setting of the above-mentioned blank Channel is not possible

It is, on the other hand, an arrangement for tuning a television receiver to the output channel of one RF converter in a recording and / or playback device according to the type mentioned (DE-OS 20 55 941) known. In this arrangement, the circuit for generating the artificial video signal is an oscillator that generates a pulse whose repetition frequency is twice as large as the ho'izoniale Sampling frequency, this pulse used as an RF converter to discriminate the output signals AM modulator is used. This artificial one Video signal has a pulse peak value that is the peak value of the horizontal sync signal corresponds, which leads to the fact that the artificial video signal is reproduced as a black stripe image, the runs horizontally in a central position on the white background of the screen.

When this artificial video signal is used, however, there arises a problem that the Adjustment range of the required for precise tuning of the tuning device in the television receiver is, for the level of the output signal of the AM modulator is quite tight. Because the repetition rate of the pulse is twice as large as the horizontal scanning frequency, is at low levels of the output signal r? er horizontal synchronization process in the television receiver is unstable, so that an image on the screen begins to shake sideways, while at higher levels of the output signal distortion in an intermediate frequency amplifier stage arise, whereby disturbances occur in the reproduced picture on a white background, as well as fading phenomena with black stripes. As a result, precise tuning of the tuning device of the TV receiver impossible.

It is, on the other hand, a; Circuit for generation a signal known (DE-AS 12 26 144), which has a vertical marking line (line of different Luminance) only at the top of the television screen for voting. However, this signal contains not the synchronizing signal and it is therefore not an artificial video signal in its structure and function, as it is used / ends in the arrangement of the type mentioned at the beginning.

The invention is based on the object of an arrangement for tuning a television receiver to the output channel of an RF converter in a recording and / or reproducing device to create the allows an exact coordination with a simple structure.

This object is achieved by the features of the characterizing part of claim 1.

The artificial video signal according to the invention contains negative pulses and positive pulses or Frequencies of both negative pulses and positive pulses that are either equal to one vertical scanning frequency or a horizontal scanning frequency and it will be the ratio of the The peak value of the positive pulses is substantially equal to the peak value of the negative pulses made seven to three This artificial video signal is more like an actual video signal than that artificial video signal that is used in the known device (DE-OS 20 55 941). Amazingly however, a circuit for generating the artificial video signal is proportionate in structure simple.

In the artificial video signal according to the invention, the negative pulses form a synchronizing signal and the positive pulses an image signal. Thus, the artificial video signal creates an image in which a white Stripes appear on a black background. Furthermore, since the negative pulses have a repetition frequency that is the same as that of the synchronization signal will be the "synchronization of the television receiver stable and does not become unstable if the level of the output signal of the RF converter decreases significantly As a result, the positive pulses form a white stripe in a relatively small area on the black background of the TV screen, even if the value of the output signal of the RF converter is relatively large, so that a certain distortion in the intermediate frequency amplifier stage arises, the interfering image is superimposed on a black background and therefore less prominent. Adjustment is not difficult if the level of the output signal of the HF converter is particularly high. Consequently, by using the artificial video signal, after the invention the possible comparison for the level of the output signal of the RF converter further than in Use of the artificial video signal according to DE-OS 20 55 941.

In the artificial video signal of the present invention, the width of the positive pulse can be can be selected regardless of the width of negative momentum to any value within a wide range. Furthermore, the The width of the positive pulses can be chosen so that the white stripe on the television screen is better appears recognizable.

Developments of the invention, in particular the circuit for generating the artificial video signal are characterized in more detail by the subclaims.

Exemplary embodiments of the invention are described below with reference to the drawings, for example. It shows

F i g. 1 shows a block diagram of an embodiment of the deafness arrangement according to the invention,

Fig. 2 is a circuit diagram showing an embodiment of the discrimination signal generating circuit used in the arrangement according to the invention;
3 (A) to 3 (H) are curves of signals as they are present at the various points in the circuit according to FIG. 2,

Fig. 4 (A) and 4 (B) are schematic representations showing the a discrimination signal of the circuit according to FIG show on a screen of a television receiver and the curve of this signal,

F i g. 5 is a circuit diagram of the circuit for separating the Synchronization signals,

F i g. 6 (A) to 6 (D) are schematic curves for

Description of an example in which the white level pulse is not in the right place on the discrimination signal.

F i g. 7 is a circuit diagram of an embodiment of FIG Discrimination signal generator circuit. which has been used in the arrangement according to the invention,

Figs. 8 (A) through 8 (H) are waveforms of signals showing at various points in the circuit according to FIG. 7 exist and

F i g. 9 is a schematic representation of an image e ^ .nes discrimination signal which is generated by a circuit according to FIG. 7 is reached on the screen of a television receiver.

In Fig. A device VTR IO is connected on the one hand to an antenna II and on the other hand to a television receiver 13 via a switch 12. The switch 12 establishes a connection with its contact a . when the television receiver 13 receives a signal received from the antenna 11, and it connects to another contact b . when it receives a signal from the VTR 10 device. The device VTR 10 primarily contains a recording and reproducing device 14 to record the signal from the antenna II and to reproduce the signal recorded on a tape, a discriminating signal generator circuit 15 for generating an artificial video signal for discrimination, as discussed below, and a RF l'msetzer 16 of the \ usgangssignal of Aufzeichen- and / or reproducing apparatus 14 and the circuit 15 to an I ^r FREQUENCY implements which are suitable for supply to the television reception ';' I 3 is suitable.

The operator of the VTR 10 device ■. c-rbmJet before using the device for the first time \ TR 10 with the television receiver 13. which makes the Artificial video signal of the Discminteningssignalgene - ',! gate circuit 15 supplied to the television receiver 13 for discrimination via the HF converter 16 wrd The operator then turns a channel select tuning knob a. whereby a ν changeable \ *. Mind of an electronically tunable F.mpfänt'O's is set, which is in the television receiver 13 is built in. until an image m: t a certain grid according to the artificial video signal described in "bon is displayed on the television screen to discriminate When a certain picture pattern has been generated on the screen. the manipulation is used to [turn on the channel selection voting terminated, and the resulting matched state wi ^ d on an appropriate empty channel that is not used as a broadcast receiving channel. It will be a consequence of this afterwards possible, the output from the device VTR 10 To reproduce the signal on the screen of the television receiver 13 by changing the preset Selects channel.

In the following, an embodiment of the discminator signal generator circuit 15 will now be given with reference to FIG. 2 described. A power transformer 20 is connected with its primary winding to the general alternating current network. The alternating voltage taken from the secondary winding of the power transformer 20 is rectified in a single-phase, fully rectifying bridge circuit 21. and it is then fed to a voltage regulator 21. to which a certain stable DC voltage is emitted

From a point P in de-rectifying

Bridge circuit 21, an alternating voltage a is derived, as shown in FIG. 3 (A) is shown. and this voltage is then voltage divided by means of resistors R I and R 2 . The divided voltage thus obtained is fed to the base of a transistor Tr 1. The transistor TrI assumes the conductive state when the voltage supplied to its base is greater than its threshold voltage, consequently the curve of the base voltage b of the transistor TrI is as follows. as shown in FIG. 3 (B) is shown. The collector voltage c of the same transistor Tr I has a curve. as shown in Fig. 3 (C). and it is substantially zero during the I IN period and has a voltage which is substantially equal to the ^{DC output voltage (+ VV / 1 of} the voltage regulator 22 during the AlJS period of the transistor Tr I.

The Kollektor.iiisgangsspannung c of the transistor Tr I is by means of a first differentiating circuit 22. ine a capacitor Π and a resulting differentiated pulse waveform d shown in Fig. 3 (D) and it is supplied to the base of the transistor Tr 2. At the same time, the collector output voltage c of the transistor TrI is differentiated with the aid of a second differentiating circuit 24, which contains a capacitor C2 and a resistor R 4 , and the resulting differentiated pulse waveform e, which is shown in FIG. 3 (F.). is then fed to the base of the transistor Tr 3. The time constant of the differentiating circuit 23 is smaller than that of the differentiating circuit 24. As a result, the width of the differentiated pulses rf is narrower than that of the differentiated pulses e.

The transistor 772 only becomes non-conductive when it is supplied with the pulses of negative polarity of the sequence of differentiated pulses d. As a result, a pulse becomes f shown in Fig. 3 (F). derived from a connection point between the resistors R 5 and Rh , which are connected in series with the collector of the transistor Tr 2. The transistor 7> 3 is only switched to the conductive state when the pulses of positive polarity of the sequence c of differentiated pulses are fed to it. Consequently, from a connection point between the resistors R 7 and RS. which are connected in series with the collector of the transistor Tr 3 , derived a pulse train g , as shown in Fig. 3 (G).

When the video signal conforms to the National Television System Committee standards. then a standard alternating current source with a frequency of 60 Hz must be used. On the other hand, uann must. If the video signal is designed according to the standards of the PAL system or the SECAM system, a conventional AC power source with a frequency of 30 Hz can be used. Consequently, the time periods of the above pulse signal shapes / and g are equal to one vertical scanning period (1 VSP) of the video signal. Which has been picked up by the television receiver 13.

The pulse signal sequences / and g go through a DC blocking capacitor C'3 and a mixing resistor /? 9 and through a DC blocking capacitor C 4 and a resistor R 10. They are then mixed with one another, resulting in a signal h as shown in FIG . 3 (H) is shown. The resistance values of the mixed resistors R9 and R 10 are dimensioned so that the ratio of a peak value

tes of a positive momentum f \. taken from the pulse train f , to a peak value of a negative pulse g \ taken from the pulse train g. together in the signal h becomes 7: 3. In the signal h , the peak value of the pulse / Ί is substantially equal to the peak value of the vertical synchronizing signal. As a result, the signal h becomes an artificial video signal having a peak white of a suitable width existing at a single point during the vertical scanning period, and this signal is used as a signal for discrimination.

This signal Λ for discrimination is made with the help of of the RF converter 16 to a certain frequency · converted. That way in frequency converted signal is transmitted through an output terminal and with the aid of switch 12 to the television receiver 13, as shown in FIG. 1 is shown. fed. For the free channel ties television receiver 13 is now a Absliipin process of the type mentioned above for the / ured in the frequency converted signal executed.

If the television receiver 13 is precisely tuned to the discrimination signal Λ, then a very specific image appears on a screen 30 of the television receiver 13, as shown in FIG. 4 (A) is shown. A white stripe 32 runs across a black background 31 on the screen 30, which means that when this pattern occurs on the screen, the empty channel of the television receiver 13 is appropriately matched to the output frequency of the RF converter 16 in the VTR 10 device. So Wenii the screen is observed by an operator, the tuning process for the empty channel of the television receiver 13 can be carried out very easily and quickly via the RF converter 16. Referring to Fig. 4 (B), there is shown the signal h shown in Fig. 3 (H) in relation to that of Fig. 3. 4 (A) screen.

If, after a certain empty channel has been tuned in the manner described above, the The playback mode of the device VTR 10 is turned on, then an operator selects the empty channel preset in the manner described above. the end. and places it at the voting facility of the television receiver 13. The reproduced signal is then taken from the recording and / or playback device 14 of the device VTR 10 is supplied from the connection 25 to the RF converter 16 and the reproduced RF signal output at terminal 26 is then sent to the television receiver 13 is supplied and it is displayed as an image on the screen.

The discrimination signal h is preferably designed so that the pulse f \ is there so that there is an intermediate time T between this pulse / i and the previous pulse g \ which is significantly less than a third of a vertical scanning period. The reason for this will now be explained described below.

In general, there is a synchronizing signal separating circuit in the television receiver 13 which is constructed like the circuit of FIG. 5. The video signal which is fed to an input terminal 40 is held at a fixed value by means of a capacitor C6 and a diode D and it is then fed to the base of a transistor Tr 4. A separate synchronization signal is derived from the collector of the transistor Tr 4 and via an exit

final 41 submitted.

It is assumed here that the pulse f \ for the peak value of white is at a distance from the preceding pulse g \, which corresponds to the vertical synchronization signal, which is greater than a third of the vertical synchronization period as in the case of the signal h, which is shown in F i G. 6 (A) is shown. Then, the waveform of a signal which is fixed by the capacitor Cd and the diode D and which is then supplied to the base of the transistor Tr4 becomes as shown in Fig. 6 (C). If the signal h has a horizontal synchronizing signal 42 as shown in Fig. 6 (B), this signal is certainly held at a fixed value. However, since the present embodiment is so designed. that the discriminator signal h is achieved by a circuit arrangement which is as simple as possible, then the signal / ι. which is actually achieved do not contain a horizontal sync signal 42, as shown in FIG. 6 (A) is shown. Therefore, an inevitable drop will occur in the signal supplied to the base of the transistor Tr4, as shown in FIG. 6 (C). Accordingly, on the other hand, the signal output from the output terminal 41 contains an undesired pulse 43b at a position corresponding to the white signal h in addition to a pulse 43.7. which is present in accordance with the pulse g \ of the original vertical synchronizing signal, as shown in FIG. 6 (D) is shown. This means that in a normal vertical scanning period an incorrect vertical synchronizing signal is additionally present, which leads either to a vertical fluctuation of the white picture strip 32 on the reproduced picture or to a lost picture due to irregular vertical synchronizing signals. An experiment has shown, however, that when the pulse h is present at a location less than a third of the vertical scanning period from the pulse gi before it. no unwanted pulse 436 is formed even if the sagging described above occurs.

Referring to FIG. 2 can be recognized. that a switch 27. which is switched into the power supply line of the voltage regulator 22 is a manually operated switch. which is normally kept open and which is only closed when the process of channel discrimination is to be carried out and when the tuning process to the output frequency of the RF converter is to be carried out. On the other hand, a manual switch 27a can be provided between the base of the transistor TrI and ground in place of the switch 27, and this switch is shown in broken lines Transistor Tr 1 to ground. Furthermore, instead of these manual operating switches 27 and 27a, switches can be used which are alternately opened and closed in accordance with the tape cassette loading process for the recording and / or reproducing device. Furthermore, another circuit arrangement can also be used in which the manual switch and the switch which is controlled in accordance with the tape cassette loading process are connected in series or in parallel.

The pattern of the displayed image of the artificial video signal for discrimination is not on the image a single white stripe, like the one above

Embodiment limited, but it may be some other appropriate picture or picture pattern. the Rectifier circuit 21 and voltage regulator 22 can usually be used as a DC power source for the Device VTR 10 can be used.

Another embodiment of the discrimination signal generator circuit according to FIG Invention in connection with FIG. 7 described.

An astable r.'jltivibrator 50 generates as an output signal at its output terminals 51a and 516 square-wave signals a and b, the polarities of which are opposite, as shown in FIGS. 8 (A) and 8 (B). The oscillation frequency of the astable multivibrator 50 is set to a frequency equal to the frequency of the horizontal sync signal, that is, 15.75MHz for systems that operate according to the US National Television System Committee standard and 15.625 MHz for systems which work according to the PAL and the SF.CAM system.

The square-wave signal a, which is output at the output terminal 51a, is differentiated in a differentiating circuit 52 which contains a capacitor C 10 and a resistor R 20, whereby a pulse c is produced which has a curve, as shown in FIG. 8 (C). The differentiated pulse c is then passed through an inverter 53, in which its pulses of positive polarity are inverted and shaped so that a pulse d arises, as shown in FIG. 8 (D) is shown.

Accordingly, the rectangular signal is b, which is discharged b at the output terminal 51, is differentiated in a differentiating circuit 54 which includes a capacitor Cll and? Inen resistance R 2t, arises whereby a pulse e having a waveform as shown in Fig. 8 (E). The differentiated pulse e is then passed through an inverter 55, in which its pulses of positive polarity are inverted and their course is shaped in such a way that a pulse f. As shown in FIG. 8 (G) is shown. arises.

The peak values of the pulses c / and g are set by means of mixing resistors R? 2 and R 23 and the pulses then pass through capacitors C12 and C13, and they are then mixed at a connection point 57 so that a signal a. as shown in Fig. 8 (H). arises. In this case.

As in the previous case, the resistance values of the mixing resistors R 22 and R 23 are chosen so that their values give a ratio of the peak value of a positive pulse g \ of the pulse g

j to a peak value of a negative pulse d \ of the pulse d, both of which are in the signal h , of 7: 3 is reached. In the signal h , the peak value of the pulse £ ί is substantially equal to the peak value of white of the video signal and the peak value of the

in pulse dt is substantially equal to the peak value of the horizontal sync signal. Thus, the resulting signal h is an artificial video signal which has both the pulse d \ , which is regarded as the horizontal synchronizing signal, and the pulse

ι - ■> g \. which is seen as a white signal.

The above signal h passes through a closed manual switch 58 and is fed to an output terminal 59. The output signal h is fed to the RF converter 16, and it is then the

? n television receiver 13 supplied. When the television receiver 13 g -'- exactly on the output signal frequency of the HF converter 13 is tuned, then an image is produced which has a pattern in which a white Image strip 62 is present, which is vertically on a

2ϊ black background 61 runs.

Since the oscillation frequency of the astable multivibrator 50 is so set. that it is equal to the frequency of the horizontal synchronizing signal. as described above, each period of the pulse signals corresponds to, i.e. d \, g and g \ exactly a single horizontal scanning period of the video signal that is recorded by the television receiver 13. As a result, the white image component will appear at the same point on the screen in the transverse direction as a result of the pulse signals g \, whereby a white image strip 62 is produced which runs vertically.

The width of the pulses of the pulse e (f, g. G]) is determined by the time constant of the differentiating circuit 54. Accordingly, the width of the white image stripe 62 is appropriately adjusted by setting the above time constant to a constant value. Further, the white image strip 62 can be adjusted to a desired position on the screen by adjusting the duty cycle of the output signals a and b of the astable multivibrator 50 to an appropriate value.

For this purpose 4 sheets of drawings

Claims (4)

Fi1 If patent claims: 1. Arrangement for tuning a television receiver to the output channel of an RF converter in a recording and / or reproducing device, the reproduced signal from the recording and / or playback device is supplied to the television receiver for displaying the image and the recording and / or reproducing device a circuit for generating an artificial one Video signal for tuning having at least either horizontal or vertical synchronizing signals and wherein the artificial video signal for tuning through the RF converter is supplied to the television receiver and the tuning device of the television receiver such is set so that an image of the artificial video signal is displayed on its screen, characterized in that the circuit (15) the artificial video signal in the form of forms negative pulses and positive pulses, the frequencies of both negative pulses and the positive pulses are substantially equal to either the vertical scanning frequency or of the horizontal scanning frequency, and that the ratio of the peak values of the positive pulses to the peaks of the negative pulses is essentially seven to three and these peaks essentially correspond to the white level or the synchronous level. 2. Arrangement for voting according to claim 1, characterized in that the white value pulse (f \) is at a point tsfindet .vo the time interval compared to the artificial vertical synchronizing signal (g \) before this pulse "\) less than a third of the vertical scanning period is. 3. Arrangement for voting according to claim 1, characterized in that the circuit (15) for generating the artificial video signal for voting contains the following parts: a circuit (Tr 1) for generating a rectangular curve from a general AC voltage source with a frequency equal to that of vertical synchronizing signal frequency of the video signal, a first and a second differentiating circuit (23, 24), each of which is supplied with the voltage with a rectangular waveform and which produce differentiated pulses as an output. 4. Arrangement for tuning according to claim 1, characterized in that the circuit (15) for generating the artificial video signal for tuning contains the following parts: an oscillator (50) for generating a square-wave voltage, the frequency of which is equal to the horizontal synchronization signal frequency of the video signal, first and second differentiating circuits (52, 54) to which the square-wave voltage is fed and which form differentiated pulses as an output signal, a circuit (55, 56) for generating a pulse for the white value (f) from the output signal of the second differentiating circuit (54) , a circuit (53) for generating an artificial synchronizing signal pulse (g) from the output signal of the first differentiating circuit (52) and a circuit (R 22, Λ 23) for mixing the white value pulse (!) and the artificial horizontal synchronizing signal pulse (g) in one certain mixing ratio to thereby obtain the artificial video signal for tuning .