JPS5862983A - Antenna switching circuit for video tape recorder - Google Patents

Abstract

PURPOSE:To prevent the generation of the high level rasping noise, by switching a stereo program to a TV program from an external antanna with a prescribed time of delay from the switching operation, through the operation of a mode setting switch. CONSTITUTION:A switch control circuit 23 automatically controlling the set position of switches 21, 22 is provided in response to the set position of a switch 20. The circuit 23 sets the switches 21, 22 to positions 21a, 22b when the switch 20 is connected to a position 20a, to provide a modulation signal from an RF modulator 19 to an output terminal and to provide a control signal from a control signal source 17 to an encoder 18. On the other hand, in selecting the switch 20 from the position 20a to the position 20b, the switch 22 is set to the position 22b to interrupt the control signal, and the switch 21 is set to the position 21b with a prescribed time of delay to provide an ON-AIR signal to an output terminal.

Description

[Detailed Description of the Invention] The present invention relates to an antenna switching circuit for a video tape recorder (VTR), and its purpose is to suppress an increase in the noise level generated during switching ◇ Television (TV) ii) The TV receiving the voice multiplexed signal is automatically set to a mode that is compatible with the sales strap depending on the strap (stereo, bilingual, or hexanoral) of the TV audio multiplexed signal. korta,
As is well known, this is achieved based on the presence or absence of the control signal in the TV audio multiplex signal and the difference in frequency.
It is known that there is a response delay of about seconds. For example, in response to the response delay f'L of a TV receiver, this method operates the mode setting switch of the antenna switching circuit of a VTR and maintains the stereo program at the output terminal of the circuit. This becomes a problem when trying to provide an on-air signal to the antenna terminal η. Since the tuner of the TV receiver is set to an empty channel to receive the VTR modulator output, after the above operation, no carrier wave is received and noise is generated on the screen of the TV receiver and its speakers are By the way, this noise f
The TV receiver is stereo (and bilingual).
When set to monaural mode, the output is larger than when set to monaural mode, as it picks up noise from the audio subchannel system. Therefore.

Taking advantage of the above response delay, an abnormally high level of noise is generated for a short period of time corresponding to the delay time.

In the conventional Lg circuit shown in Figure 1, when the mode setting switch m is set to the real position, the changeover switch i21 f154 is set to the solid line. In addition, the output terminal for the TV receiver: S+ is given with the variable signal of the 41VCRF modulator (5), and the encoder (6: the output is a 4M audio multiplex signal that outputs stereo programs. If you set the TV receiver to stereo mode, you can enjoy a stereo program with virtually no noise level as shown in period d in Figure 2.
When the switch is set to 1tfL (not shown), the switch +21 is also switched to the position shown by the broken line.

The on-air signal from the external antenna + 712)) is applied to the output terminal (4), and the TV receiver (3) is set to the channel of the tuner, so for example, the carrier 1cm reception is possible. The reception mode is set to stereo mode during the B period to compensate for the response delay described above, and remains at f'Lπ, so during this B period, Bokke 11 TV reception 1#! The king of the dead, the noise that occurs in the sub-audio channel system NM, N8 f will be output 0 After that, the TV
When the image is received poorly, it is converted to monaural mode and only the miscellaneous fHM is output. (Refer to Figure 2 M group C). Next.

If it is set to the channel of TV 9 [11k131 Chinaina t on-e-dong], it will not be able to receive the above-mentioned on-air signal, so neither the upper level fNM nor N8 will be output as if it were a real sparrow (see period 1klD). Note that the timing of switching the operating mode of the TV receiver (3), that is, switching from monaural mode to on-air mode, will be delayed by the amount of the response delay described above, but this delay is not actually a problem. To,
``In the conventional circuit, the noise level fluctuates greatly when transitioning from period B to period C, resulting in pulse-like noise that is difficult to hear.

The present invention aims to suppress the noise level during this period B to prevent the generation of harsh noise. 6.6.
In other words, while viewing a stereo program on the VTR, operate all the mode setting switches on the VTR to watch the program on the external antenna 2)-ra's on-air 4M t-TV receiver 1a.
When applying it to the machine, at the same time as the operation of the
Since f& is realized, the above-mentioned drawbacks are improved by realizing the imparting without any delay, but after a delay fL which is longer than the time corresponding to the above-mentioned response delay.

The present invention will be described below with reference to illustrated embodiments. Figure 3 shows the configuration diagram of the antenna switching circuit of V'I'H that is included in the present invention.
It is shown together with an external antenna and a TV receiver connected to the TR, and FIG. 4 is an explanatory diagram of the operation of the circuit. In the figure (10Hv TR, Qll means external antenna, 11
3 is a TV receiver, with an external antenna fllllHvT
nQOl) completed ff terminal [1314C connected, also 'I' v receiving m*t121i, t V T Rtl(1
17) Output terminal aattca is connected. With the U-μTV signal source, the video signal recorded on the video track of this nH video tape is extracted and converted into a standard T-video signal using well-known techniques.
This is an audio signal source having a means for reconstructing it into a V4@ number, and is provided with means for generating an audio signal tS of the f'Lfc1 or a2 channel recorded on an audio track on a videotape. Q71ball1l m 4l
41982.5 on the stereo program.
Hz, in a baingal program, a sine wave (wave signal) of 9'22.5Hz is generated.
iz T V audio multiplexing (an encoder for synthesizing gibberish sounds)
Reception of control information from signal source 1.

Depending on the type of the smart signal, all the audio multiplexed signals representing stereo or bilingual programs are output.

-Also, when the control signal is not inputted, a TΩΩ audio multiplied signal representing a monaural program (same as normal TV audio) is output. (1!II is an RF modulator,
This fL has a TV43 signal source (standard TM01 from 151 and an encoder (11117D> et al.'s TV audio multiplexing Ij) and a TV receiver l) 21 of 2: & channel receives 4M, FM It outputs a memorial service.

12L) A first switch that sets the output mode of HVTRI□, and a first position (2L]a) that instructs the first switch to output the modulated signal from the RF modulator [j], and a Rin 2 commands the output of on-air signals
The position 1i (20b)e is configured to be selectively selected. Answer 6 to 11 Switch Shun's command to the woman and if+1
This second switch Uv
ay, 1st place 1i (21a) and RFf Seiki 19 changes -
External antenna tll1 at the 1st island trap 2nd position (2ib>
21) - Output terminal 1141
0e that I am trying to transmit to the TV receiver Q3 through
i4rt' is an lX5 switch that is controlled in response to a command from JX1 switch 4, which is in the first position (22 m)
:'-/'An ms scratch signal is given to f181, and this provision is blocked at the second position (22b)-t'◇
eAa depending on the setting position of the first switch (7)
In the switch discount (2) path, which automatically controls the setting position of 1@ of the ll13 switch, immediately set the 1st position as shown in the figure. Second. Third
The transistor 94t#-, the IP control circuit, and the coil (2) that activates the third switch II) (2).

and biasing means for each transistor.
(1) A manual stereo (or bilingual) or monaural operation switching switch, the first device L50 shown in the figure.
Stepping into the second position (sob) instead of a) forces the monaural mode by using VC. Next, we will explain the operation of this circuit. Each transistor 4 (E)) is made conductive, and each coil i! 44 is given an excitation type fL, and the 512.213 switch @@woizn is also kept at the first position ft (21a) (22a).

Therefore, the encoder (181 has a σ control i1 signal source +1
The control signal from 71 is applied, and the T'V audio multiplex signal of the stereo (or bilingual) program is modulated by the R'FKm unit Q9. It will be transmitted. Then, as shown in period A in Figure 4, a stereo (or bilingual) program is output to the NFC'RV receiver machine A2, which is set up on the NFC'Rv receiver in order to set fL≦(I. do.

From this state IIη1, move the first switch ``■'' to the second position (20b
), the first and third transistors Cl4M immediately turn into non-conducting states, so the third switch 4 changes to the second position 1c2'zb), and no control signal is applied to the encoder U&. The circuit is configured such that it is turned into a non-conducting state after a delay of one time T (see Figure 4) due to the delay circuit 4 (in the second transistor). TV audio multiplex signal without any ID signal before passing (contains the carrier of -channel)
is modulated by the RF modulator u9 and continues to be applied to the TV receiver 11C121. This TV receiver (12+) receives a command to switch from stereo (or bilingual) mode to monaural mode due to the lack of a control signal, but due to the above-mentioned response delay, the stereo (or bilingual) mode continues for period B in Figure 4. ) mode. However, during this period B
Since vc is configured to receive the modulated signal from the RFf-device αl, it does not output miscellaneous fNM, M- or fL.

This period in which both noises are not output continues until the time T elapses when the second switch (2) is set to the second position (21b). That is, the time T is set to be longer than the response delay time, and during the difference period C1, substantially no noise is output to the UTV receiving m pupil. After the delay time T has elapsed, the second switch (2) of the frame is switched to the second position (21b), and the on-air signal from the external antenna aB is applied to the TV receiver α8. , because the tuner is installed on an empty channel, the carrier wave is not received, and the noise NM generated in the audio channel system is during period 02.
output across the entire range. After that, when the tuner of the TV receiver (13) is set to the on-air channel, the carrier is transmitted to the main audio channel system, so the occurrence of miscellaneous fM is suppressed (see period 4). , the TV receiver (121'#IhrF) is switched to the on-three mode after a delay due to the response delay described above.

As explained above, there is a state in which a stereo program on a circuit frame VTR according to the present invention is viewed on a TV receiver.
When operating the mode setting switch to apply the on-ear signal from the external antenna to the T-TV receiver 4a, it takes one hour from η to the sales operation. ! Give 5I after f'Lt! Because I'm making it one of the most visible.

It is possible to suppress the output of high-level harsh noise based on the mode switching response delay f'LK in the TV receiver fIIJ11, which is useful without causing discomfort to the viewers.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional circuit, and Figs. 1 and 2 provide an explanation of its operation. Figure 3 shows the construction diagram of the circuit of the present invention, and the operational layout of each frame in Figure 4. King - Book explanation (to)...1st switch, I...External antenna,
0IJ-RF transformer, t13...TV receiver, @...
・IJIE2 switch. Akane... back door signal #, aη... control signal source, special
...Encoder, @..., J! 3 switches, (2)・
・Switch control wholesale circuit O

Claims (1)

[Claims] 1. The first step is to set the output mode of the video tape recorder.
Switch and external antenna! IiI! The on-air signal from the antenna terminal η and the variable signal from the RF [J@ equipment are transferred to the TV receiver! a second switch for selectively transmitting the signal to the output terminal connected to the RFR 11a; an encoder for synthesizing audio multiplexed signals; a third switch for applying a control signal from the control signal generation source to the encoder; The installation position of the third switch is equipped with a switch-side leg circuit that automatically operates the switch, and the sales switch control outlet is connected to the above-mentioned switch! ll! When connected to the 1st position, the 2nd. Each of the three switches 3 is set to the first position to apply the variable m signal to the output terminal, and also to apply the -control (d) signal to the output terminal.
A sound signal is applied to the encoder, while when the tomb 1 switch is connected from the tgag1 position to the second position, the fifth
The switch is set to the IK2 position to cut off the assignment of the first control number, and the second switch is set to - after a time delay.
An antenna switching circuit for a video tape recorder, wherein the antenna switching circuit for a video tape recorder is configured to set the on-air signal to the output terminal.