JPH0115007Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention relates to a reference signal switching device for a servo circuit in a recording/reproducing device, and particularly for switching a reference signal for a phase control system of a servo circuit in a VTR that serves as a recorder in an electronic editing system. Regarding equipment.

Conventional technology It has been known to prepare two or more VTRs and perform electronic editing by inserting and recording video signals played by another VTR on a pre-recorded magnetic tape, or by recording spliced footage. .
FIG. 1 shows a block system diagram of an example of a general electronic editing system. In the figure, a video signal and an audio signal reproduced from a recorded magnetic tape by a reproducing device 1 are transmitted to a video signal input terminal 6V and an audio signal input terminal 6A of a recording and reproducing device (VTR) 5 via output terminals 2V and 2A, respectively. while being supplied to the monitor device 7. The playback device 1 is supplied with a control signal from the controller 4 to its remote control terminal 3, and the recording and playback device 5 is supplied with a control signal from the controller 4 to its remote control terminal 8, thereby controlling its operation.

The recording/reproducing device 5 splices or inserts the reproduced video signal and reproduced audio signal from the input terminals 6V and 6A into a position on the magnetic tape intended by the editor. In order to search for the recording position of the video signal and audio signal to be electronically edited, the reproduced video signal and the reproduced audio signal of the reproduction device 1 are monitored and reproduced by the monitor device 7. In addition, at the edit point at which the recording/reproducing device 5 should start splicing recording or insert recording, the recording/reproducing device 5 is set in the playback mode in advance, and the reproduced video signal and the reproduced audio signal are sent to the monitor device 1 via the output terminals 9V and 9A.
0, and the monitor reproduces the search result. Furthermore, the monitor device 10 can also monitor and reproduce the reproduced video signal and reproduced audio signal from the recorded magnetic tape after electronic editing, thereby making it possible to confirm the results of electronic editing.

In addition, the terminal 12 of the playback device 1 and the recording/playback device 5
An external synchronization signal is supplied to the terminal 13 of the input terminal 1 from an external synchronization signal generator (not shown) via the input terminal 1.

Here, the recording/reproducing apparatus 5 has conventionally been provided with a changeover switch (sync switch) for arbitrarily switching the reference signal of each phase control system of the head servo circuit and capstan servo circuit. This switch is a switch for switching between an external mode (hereinafter referred to as EXT mode) that gives top priority to an external synchronization signal and a video mode that gives top priority to a playback video signal from the playback device 1. When the mode is selected, the external synchronization signal is used as the reference signal for the servo circuit when an external synchronization signal is input, and the vertical synchronization signal of the playback video signal is used as the reference signal when no external synchronization signal is input. When none of these are input, the output signal of the internal oscillator is output as the reference signal. Also, when the video mode is selected using the above switch, the vertical synchronization signal of the playback video signal is used as the reference signal, and when this playback video signal is not input, the internal oscillator is activated regardless of whether an external synchronization signal is input. The output signal is used as the reference signal.

Problems to be Solved by the Invention When the above changeover switch selects the video mode, or when the EXT mode is selected but the external synchronization signal is not input to the input terminal 13, the recording/playback device 5 When performing normal playback, when the playback device 1 is in variable speed playback mode, the playback device 1 is connected to the video signal input terminal 6V.
A variable speed playback video signal is supplied, and its vertical synchronization signal is used as a reference signal for the servo circuit of the recording/playback device 5. However, in the above case, noise bars are present in the variable speed playback video signal, and the time width of one field is not a normal value, so the servo circuit of the recording/playback device 5 may malfunction or may not operate normally. However, there were problems such as the reproduced image on the monitor device 10 being distorted.

Therefore, the present invention uses the aforementioned changeover switch to preferentially use the output signal of the internal oscillation circuit as a reference signal for the servo circuit during playback, and to give priority to the vertical synchronization signal of the playback video signal or its frequency-divided signal during recording. A standard for a servo circuit in a recording/reproducing device that solves the above problems by having a configuration that further selects the mode used as the reference signal (hereinafter referred to as internal mode (INT mode)). The purpose of the present invention is to provide a signal switching device.

Means for Solving Problems The present invention includes a changeover switch that outputs a signal when internal mode is selected, and a changeover switch that switches between recording mode and playback mode and selectively outputs the signal of the changeover switch only during playback mode. an oscillation circuit that oscillates and outputs a frequency signal related to the vertical synchronization signal frequency; an output signal of the oscillation circuit is selectively output as the reference signal according to the output signal of the first switch circuit; a second switch circuit that selects and outputs the vertical synchronizing signal in the externally input video signal or its frequency-divided signal as the reference signal in priority to the output signal of the oscillation circuit in a recording mode in which no signal is output from the first switch circuit; The second embodiment is constructed from the following.
This will be explained with reference to the drawings below.

Embodiment FIG. 2 shows a block system diagram of an embodiment of the device of the present invention. In the figure, the changeover switch 15 is a switch that is turned on only when the sink switch is switched to the INT mode selection position. is applied as a switching signal, and this is switched and connected to the terminal 18a side. The terminal 18a is connected to an input terminal 19, and a high level signal is input to the input terminal 19 only when the sync switch is in the EXT mode position.

The above-mentioned sync switch is one of the switches provided on the lower side of the front panel of the recording/reproducing device 20 to which the device of the present invention shown in FIGS. 3 and 4 can be applied.
It is a switch indicated by 21. As shown in FIG. 4, this sync switch 21 has EXT mode position "EXT", video mode position "VIDEO", and INT mode position "INT".
A total of three positions (switching positions) are provided, and any one of the three modes, EXT mode, video mode, and INT mode, can be arbitrarily selected. As described above, these modes define the reference signals in the recording mode and reproduction mode of the phase control system of the servo circuit of the recording and reproducing apparatus 20 that performs electronic editing and the like.

In FIGS. 3 and 4, 22 is a search dial for arbitrarily determining the playback speed and playback direction during variable speed playback, 23 is a cassette insertion/extraction hole opening/closing door, and 24 is a power switch.

Returning to FIG. 2 again, the input terminal 25
is an external input video signal input terminal corresponding to the input terminal 6V in FIG. 1, and input terminal 26 is an external synchronization signal input terminal corresponding to the input terminal 13 in FIG. The input signals of the input terminals 25 and 26 are sent to the synchronous separation circuit 2.
After the horizontal synchronization signal is separated and extracted from 7 and 28,
The signal is supplied to terminals 31a and 31b of a switch circuit 31 through amplifiers 29 and 30. Further, the output horizontal synchronization signal of the synchronization separation circuit 28 is supplied to the rectification circuit 32. The rectifier circuit 32 is a circuit that generates a switching signal for the switch circuit 31, and when the switch circuit 18 is connected to the terminal 18b side and a high level signal is supplied from the input terminal 19,
That is, only when the sync switch 21 is placed in the EXT mode position, it rectifies the input horizontal synchronizing signal and generates and outputs a switching signal that connects the switch circuit 31 to the terminal 31b. sink switch 21
When the switch circuit 3 is placed in either the video mode position or the INT mode position, the rectifying operation is disabled and the switch circuit 3
It generates and outputs a switching signal that connects the terminal 31a to the terminal 31a.

The horizontal synchronizing signal taken out from the switch circuit 31 is passed through an inverter 33 to a low-pass filter 34.
The vertical synchronization signal is separated and extracted here. The vertical synchronizing signal taken out from the low-pass filter 34 is supplied to a monostable multivibrator (hereinafter referred to as "MM") 36 through an amplifier 35.
Here, it is delayed by, for example, 10 horizontal scanning periods (10H). Further, the output signal of the switch circuit 31 is applied to the M.M.38 through the differentiating circuit 37. M.M3
The output pulse No. 6 is supplied to a terminal 40a of a rectifier circuit 39 and a switch circuit 40, respectively, and is supplied to a terminal 42a of a switch circuit 42 through a differentiating circuit 41. Further, the output pulse of the M.M 38 is supplied to the switch circuit 42 as a switching signal.

The rectifier circuit 39 is a circuit that generates and outputs a switching signal to the switch circuit 40 which forms the main part of the device of the present invention, and the switch circuit 17 is controlled by the recording/reproduction mode signal from the input terminal 43.
Only when a lower level signal is supplied,
It generates and outputs a switching signal that disables the rectification operation and puts the switch circuit 40 in the input signal selection output state of the terminal 40b, and otherwise performs the rectification operation, rectifying the output pulse of the M.M36. The switch circuit 40 is switched and connected to the terminal 40a by the switching signal obtained.

Furthermore, M.M38 is configured to generate and output a pulse with a pulse width of 3/4H when triggered by an input signal, and M.M36 is configured to generate and output a pulse with a pulse width of 10H when triggered by an input vertical synchronization signal ( 10H delay). Therefore, when a video signal near the vertical blanking period of the field is input to the input terminal 25 as shown in FIG. 5A, the output pulse waveform of the M.M.38 becomes as shown in FIG. , the output pulse waveform of M.M36 is as shown in FIG. on the other hand,
When a video signal near the vertical blanking period of the second field is input to the input terminal 25 as shown in FIG. 5E, the output pulse waveform of the M.M 38 is as shown in FIG.
The output pulse waveform of the M.M36 becomes as shown in FIG.

The switch circuit 42 selects and outputs the input differential signal of the terminal 42a during the high level period of the output pulse of the M.M38 (here 3/4H), and outputs the input differential signal of the terminal 42a during the low level period of the pulse (here 1/4H) on the terminal 42b side. Switching control is performed so that the connection is switched to . Further, the differentiating circuit 41 is configured to differentiate the pulse shown in FIG. There is. Here, the fifth
As is clear from Figures B, C, F, and G, in the first field, the falling edge of the output pulse of M.M36 shown in Figure C is within the high level period of the output pulse of M.M38 shown in Figure B. On the other hand, in the second field, the falling edge of the output pulse of M.M36 shown in G in the same figure is located at M.M38 shown in F in the same figure.
is located within the low level period of the output pulse. This is because, as is well known, in order to perform interlaced scanning, the phases of the vertical synchronizing signals are made to differ by H/2 between the first field and the second field. Therefore, in the first field, the switch circuit 42 outputs a negative pulse that is phase synchronized with the falling edge of the output pulse of the M.M36, as shown in FIG. As shown in the figure, the above-mentioned negative polarity pulse is not outputted, and a high level signal is always outputted.

The negative polarity pulse of one frame period taken out from the switch circuit 42 is supplied to the muting circuit 45 through the low-pass filter 44, where the pulse width of the high level period is a constant value of 30 ms as shown in FIG. 6B. is converted to The muting circuit 45 is a malfunction prevention circuit that does not operate even if a pulse is input during this 30ms period, and its output pulse is transmitted to the waveform shaping circuit 4.
As shown in FIG. 6C, it is converted into a pulse that is at a low level for a certain period of time (for example, 11.3 ms) from the time when the negative polarity pulse is generated from the output of the switch circuit 42, and is further supplied to the switch circuit 48 through the differentiating circuit 47. Supplied. Note that the waveform shaping circuit 46
is a circuit that determines the sampling position of the trapezoidal wave shown in FIG. 6E in the switch circuit 48.

As shown in FIG. 6E, the switch circuit 48 generates a trapezoidal wave generated from an output signal from an output terminal 59, which will be described later, with a period of two fields (one frame) and which is output when the first field is input. One field period (first field) in which a trapezoidal wave is output from the input terminal 49.
is turned off, and turned on during one field period (second field) at a low level. Therefore,
During one field period when the switch circuit 48 is on, no differential pulse is originally supplied from the differentiator circuit 47, but during one field period (first field) when a trapezoidal wave is generated and output, the input image of the input terminal 25 is When the second field of the signal (shown in vertical scanning period units in FIG. 6A) is input, a differential pulse is input from the differentiating circuit 47 during the ON period of the switch circuit 48, and therefore, this differential pulse is applied to M.M 50 through switch circuit 48 to trigger it. This allows MM
50, a certain period of time (for example,
15ms) A high level pulse is output and supplied to the terminal 52a of the switch circuit 52 through the differentiating circuit 51.

The switch circuit 52 receives a switch signal from an input terminal 53 obtained when the framing servo switch 60 shown in FIGS. 3 and 4 is on.
It is connected to the terminal 52a side, and when the switch 60 is on, it is connected to the terminal 52b side. Further, the switch circuit 54, which is connected to the common output terminal of the switch circuit 52 and is a main part of the present invention, is configured to be turned on only when a low level signal is supplied from the switch circuit 17. Therefore, the switch 60 is on, and
Only when the switch circuit 54 is off (modes other than when the sink switch 21 is in the INT mode and the playback mode), the differentiating circuit 54
The output pulse of 1 is applied to the switch circuit 56 as a low level switching signal through the switch circuit 52 and the inverter 55 sequentially, and is switched and connected to the terminal 56b side.

The switch circuit 56 is supplied with the output pulse of the M.M36 taken out from the switch circuit 40 through a low-pass filter 57, and sends this input pulse to the terminal 5.
The signal is outputted from 6a through an amplifier 58 to an output terminal 59. Here, when the switch 60 is on and the switch circuit 54 is off, the field of the reproduced video signal input to the input terminal 25 and the field of the trapezoidal wave from the input terminal 49 match. In the normal case, no signal is taken out from the switch circuit 48, so the output of the inverter 55 becomes high level, and the switch circuit 56 is controlled to be connected to the terminal 56a side, so the output terminal 59
The output pulse of M.M36 is passed through the low-pass filter 57.
A signal as shown in FIG. 6F obtained through the above is outputted as a reference signal for each phase control system of a capstan servo circuit and a head servo circuit, which will be described later. On the other hand, if the field of the reproduced video signal coming into the input terminal 25 and the field of the trapezoidal wave coming from the input terminal 49 do not match, the switch circuit 56 switches to the terminal 56b side as described above. Since the reference signal is connected, no reference signal is output to the output terminal 59.

In this way, when the recording and reproducing apparatus 20 equipped with the device of the present invention is used as a recorder of an electronic editing system like the recording and reproducing apparatus 5 shown in FIG. A known framing servo is applied to match the field order and the field order of the video signal in the recording/reproducing device 20, respectively.

Also, the sixth
The reference signal as shown in FIG.
is connected to the EXT mode selection position,
When the rectifier circuit 32 is in operation and an external synchronization signal is supplied to the input terminal 26, the switch circuit 3
1 is switched and connected to the terminal 31b side, so it becomes a 1/2 frequency divided signal of the vertical synchronizing signal of the external synchronizing signal, but if the external synchronizing signal is not supplied to the input terminal 26, the rectifier circuit 32 is in the operating state. Since there is no input, there is no output, and therefore the switch circuit 31 is switched and connected to the terminal 31a side. As a result, when a reproduced video signal is input to the input terminal 25, a 1/2 frequency-divided signal of the vertical synchronization signal is outputted from the output terminal 59 as a reference signal.

On the other hand, when the sink switch 21 is connected to the video mode selection position, the rectifier circuit 32 is deactivated and the switch circuit 31 is forcibly connected to the terminal 3.
1a, the 1/2 frequency divided signal of the vertical synchronization signal of the input reproduced video signal of the input terminal 25 is preferentially output as a reference signal, and even if the input terminal 26
Even if an external synchronization signal is received, it is never used.

Next, the capstan servo circuit and head servo circuit to which the reference signal outputted from the output terminal 59 is supplied will be explained. FIG. 7 shows a block diagram of an example of a capstan servo circuit applicable to the device of the present invention. In the figure, the reference signal enters an input terminal 61 via an output terminal 59, and is further supplied to one input terminal of a phase comparator circuit 62. The phase comparator circuit 62 constitutes a part of the phase control system, and the other input terminal is supplied with the output pulse of the frequency divider 64 through a switch circuit 63 connected to the terminal R during recording, and is supplied with the output pulse of the frequency divider 64 during reproduction. The control pulses regenerated by the control head 65 are supplied as comparison signals through an amplifier 66 and a switch circuit 63 which is connected to the terminal P, respectively.

A rotation detection signal having a frequency proportional to the rotation speed of the capstan 67 is supplied to the frequency divider 64 from a frequency generator FG 68 for detecting the rotation of the capstan motor 67 through an amplifier 69 . Further, rotation detection signals from amplifier 69 are supplied to F-V converters 70 and 71, respectively. Phase comparison circuit 6
2. F-V converter 70, 71 and input terminal 7
Each signal from 2 is sent to switch circuits 73, 74, 75.
and 76, respectively. The input terminal 72 receives a voltage corresponding to the playback speed (tape running speed) in the search mode (variable speed playback) as a reference signal for the phase control system (strictly speaking, in the search mode, the phase comparison circuit 62
Since the output of the phase control system including

Further, a search command signal is input to the input terminal 77 in the search mode, and this command signal is supplied to a switching pulse generation circuit (decoder) 78.
The switching pulse generation circuit 78 has an input terminal 77
When a search command signal is received from the inverter, that is, during variable speed reproduction, it generates and outputs a switching pulse that turns on switch circuits 75 and 76, respectively, and also supplies switching pulses to switch circuits 73 and 74 via an inverter 79. to turn these off. On the other hand, when no search command signal is input to the input terminal 77, that is, during recording and normal playback, a switching pulse is generated and output that turns off the switch circuits 75 and 76, respectively, and turns on the switch circuits 73 and 74, respectively. do.

The phase comparison circuit 62 actually has a circuit configuration that generates a trapezoidal wave from the input reference signal and samples and holds the slope part of this trapezoidal wave using the comparison signal, and the output phase error voltage is sent to the switch circuit 73. Supplied.

As described above, among the switch circuits 73 to 76, the switch circuits 73 and 74 are turned on only during recording or normal playback, so that the output phase error voltage of the phase comparator circuit 62 is the same as that of the switch circuit 73 during recording or normal playback. is supplied to the non-inverting input terminal of the mixing amplifier 80 through F-V
The output voltage of converter 70 is applied through switch circuit 74 to the inverting input terminal of mixing amplifier 80. The output voltage of the mixing amplifier 80 is applied to the capstan motor 6 through a motor drive amplifier (MDA) 81.
7, and controls its rotational speed to be constant and controls its rotation so that its rotational phase is synchronized with the input signal of the input terminal 61.

In the above capstan servo circuit, FG
A path from 68 to the inverting input terminal of the mixing amplifier 80 constitutes a speed control system, and the non-inverting input terminal of the mixing amplifier 80 is supplied with the output signal of the phase control system. In FIG. 7, a rotation direction command signal for determining the rotation direction of the capstan motor 67 is input to the input terminal 82. Further, the frequency-voltage characteristic of the F-V converter 71 is switched depending on the playback speed.

Next, to explain the head servo circuit, FIG. 8 shows a block system diagram of an example of the head servo circuit. In the figure, the output reference signal from the output terminal 59 is input to an input terminal 85, converted into a trapezoidal wave by a waveform shaping circuit 86, and then supplied to one input terminal of a phase comparator 87. On the other hand, the rotational phase of the head motor 88 that rotates the rotary body (rotary cylinder, head disk plate, etc.) to which the rotary head is attached is detected by the pick-up head 89, and the detection signal is transmitted, for example, every half rotation of the rotary body. It is taken out and supplied to M.M 90 and 91, respectively, and triggers them alternately. The pulses taken out from the M.Ms 90 and 91 are supplied to a flip-flop 92, which inverts its stable state every half rotation of the rotary body to generate one of the vertical synchronizing signals corresponding to the track scanning period of the two rotary heads. After being converted into a rectangular wave with a /2 frequency divided signal frequency (for example, 30 Hz), it is supplied to the other input terminal of the phase comparator 87 through the waveform shaping circuit 93.

The phase error voltage taken out from the phase comparator 87 is supplied to a switch circuit 94. The output terminal of the switch circuit 94 and the output terminal of the switch circuit 96 which passes or blocks the input signal of the input terminal 95 are respectively commonly connected to the non-inverting input terminal of the mixing amplifier 99. The input terminal 95 has a frequency corresponding to the rotational speed of the capstan motor 67 so that the horizontal synchronizing signal in the reproduced video signal is always reproduced at a regular constant frequency regardless of the reproduction speed in the search mode. A voltage generated from the rotation detection signal and corresponding to the playback speed in the search mode is input as a reference signal (output signal) of the phase control system.

The switching circuit 96 is controlled by a switching pulse from an input terminal 97, and the switch circuit 95 is controlled by a signal obtained from the above switching pulse through an inverter 98. As a result, the switch circuit 94 is turned on during recording or normal playback;
6 is turned off, and in the search mode, the switch circuit 94 is turned off and the switch circuit 96 is turned on.

The rotation speed of the head motor 88 is determined by a frequency generator.
A rotation detection signal detected by the FG 101 and having a frequency proportional to the rotation speed is sent to the amplifier 102, F-
Mixing amplifier 99 through each V converter 103
is supplied to the inverting input terminal of

As a result, the phase comparator 8 extracted by the mixing amplifier 99 during recording or normal reproduction.
Phase error voltage from 7 and F-V converter 103
The signal mixed with the rotation speed error voltage is
The signal is applied to the head motor 88 through the MDA 104 to control its rotation speed and rotation phase. That is, the rotational phase of the head motor 88 is made to match the reference signal phase from the input terminal 85.

In the head servo circuit with the above configuration, the path from the head 89 to the mixing amplifier 99 constitutes a phase control system, and from the FG 101 to the mixing amplifier 99.
The route leading to 9 constitutes a speed control system.

In the recording and reproducing apparatus having the above capstan servo circuit and head servo circuit, this embodiment is characterized in that the above-mentioned sync switch 21 can be connected to the INT mode position when performing normal reproduction. That is, when connected to the INT position, the changeover switch 15 shown in FIG. 2 is turned on, and a low level signal is applied to the rectifier circuit 39, making it inoperable. As a result, the switch circuit 40 is forcibly switched and connected to the terminal 40b side. As a result, the crystal oscillator 10
A signal whose repetition frequency is 1/2 times the vertical scanning frequency is taken out from the switch circuit 40 through the amplifier 107, and this signal is further supplied to the switch circuit 56 through the low-pass filter 57.

On the other hand, the low level signal taken out from the switch circuit 17 is supplied to the switch circuit 54 as a switching signal to turn it on.
As a result, the input terminal of the inverter 55 is short-circuited to the ground through the switch circuit 54, and the output circuit of the inverter 55 is always at a high level, so that the switch circuit 56 is connected to the terminal 56a side.
As a result, the output signal of the low-pass filter 57 is outputted as a reference signal to the output terminal 59 through the switch circuit 56 and the amplifier 58, respectively.

In this way, in this embodiment, when the INT mode is selected for normal playback, the output signal of the crystal oscillator 106 is used as the reference signal, so in the electronic editing system, the input terminal 2
The servo circuit can operate stably even when a variable speed reproduction video signal is received from the reproduction device.

Next, the operation when the INT mode is selected by the sync switch 21 is the recording mode. At this time, since the switch circuit 17 is connected to the terminal R side, transmission of the low level signal that enters the switch circuit 17 through the changeover switch 15 and the diode 16 to the rectifier circuit 39 is blocked. As a result, when an external input video signal, which is a reproduced video signal, is input to the input terminal 25 in this recording mode, the rectifier circuit 39
36 output pulses are to be rectified, and therefore the switch circuit 40 is switched to the terminal 40b side. As a result, a reference signal whose phase is synchronized with the 1/2 frequency-divided signal of the vertical synchronization signal of the reproduced video signal is obtained at the output terminal 59.

This means that when a reference signal is obtained from the output signal of the crystal oscillator 106 in the recording mode, the vertical synchronization signal phase and the reference signal phase of the playback video signal to be recorded (external input video signal) that has entered the input terminal 25 are This is because the switching points on the monitor screen shift because they are not synchronized accurately. Therefore, in the recording mode, the reference signal is generated from the reproduced video signal to be recorded from the input terminal 25.

Regardless of the connection position of the sink switch 21, when no input signal is supplied to the input terminals 25 and 26, the rectifier circuit 39 outputs a switching signal that switches the switch circuit 40 to the terminal 40b side. Therefore, the reference signal outputted to the output terminal 59 is a signal generated from the output signal of the internal crystal oscillator 106, thereby operating the servo circuit.

The above reference signal switching operation according to the connection position of the sync switch 21 can be summarized as shown in the flowchart of FIG. In the figure, when the sync switch 21 is connected to the EXT position, the external synchronization signal is given top priority and the reference signal generated from this signal is switched and output; when it is connected to the video mode position, the sync switch 21 is connected to the video mode position. The external input video signal is used preferentially and the generated reference signal is switched and output. Also, when connected to the INT position and in recording mode, the presence or absence of an external input video signal is determined, and if there is, a reference signal is generated from the external input video signal, and when no external input video signal is input, In the reproduction mode, a reference signal is generated from the output signal of the crystal oscillator 106 and is switched and output.

Application Example Note that the present invention is not limited to the above embodiments. For example, an oscillation circuit may generate a signal of a predetermined frequency from an oscillator (not necessarily a crystal oscillator) and a frequency divider to which the output is supplied. Of course, it is also possible to have a configuration that generates and outputs the signal.

Effects As mentioned above, according to the present invention, during normal playback, the reference signal generated from the output circuit of the internal oscillation circuit is switched and output, so it is particularly applicable to recording and reproducing devices that are the recorder side of electronic editing systems. In this case, the capstan servo circuit and head servo circuit can be operated stably regardless of whether the externally input playback video signal is a variable speed playback video signal, and when in recording mode, the externally input Since the reproduced video signal given priority over the output signal of the oscillation circuit is used to switch and output the generated reference signal, phenomena such as switching points appearing on the monitor screen (not being recorded properly) can be avoided. It has features such as being able to prevent

[Brief explanation of the drawing]

Fig. 1 is a block system diagram showing an example of a general electronic editing system, Fig. 2 is a block system diagram showing an embodiment of the device of the present invention, and Figs. 5A-H and 6A-F are respectively a time chart for explaining the operation of the block system shown in FIG. 2, and FIG. Block system diagram showing an example of a capstan servo circuit to which a reference signal from the device of the present invention is supplied, No. 8
The figure is a block system diagram showing an example of a head servo circuit to which the reference signal from the device of the present invention is supplied.
The figure is a flowchart showing the operation of the device of the present invention. 1... Playback device, 2V, 9V... Playback video signal output terminal, 2A, 9A... Playback audio signal output terminal, 5... Recording/playback device, 6V, 25... External input video signal (playback video signal) input terminal, 7,10
... Monitor device, 11 to 13, 26 ... External synchronization signal input terminal, 15 ... Selector switch, 17 ...
First switch circuit, 20...Recording/reproducing device, 2
DESCRIPTION OF SYMBOLS 1... Sync switch, 27, 28... Sync separation circuit, 32, 39... Rectifier circuit, 34... Vertical sync signal separation low-pass filter, 40... Second switch circuit, 54... Switch circuit, 59 ...Reference signal output terminal, 60...Framing servo switch, 61, 85...Reference signal input terminal, 65...
Control head, 67... Capstan motor, 68, 101... Frequency generator (FG), 8
1,104...Motor drive amplifier (MDA), 8
7... Phase comparator, 88... Head motor, 89
...Pickup head, 106...Crystal oscillator.

Claims (1)

[Scope of utility model registration request] In a device that switches the reference signal of the phase control system of each of the capstan servo circuit and the head servo circuit of a recording/reproducing device that records and reproduces signals on a magnetic tape run by a capstan using a rotating head, the signal is output when an internal mode is selected. a first switch circuit that switches between recording mode and playback mode and selectively outputs the signal of the switch only in playback mode; and a first switch circuit that oscillates and outputs a frequency signal related to the vertical synchronization signal frequency. The output signal of the oscillation circuit is selected and output as the reference signal according to the output signal of the first switch circuit, and in the recording mode in which no signal is output from the first switch circuit, the output signal of the external input video signal is A reference signal switching device for a servo circuit in a recording/reproducing apparatus, comprising a second switch circuit that selectively outputs a vertical synchronizing signal or its frequency divided signal as the reference signal with priority over the output signal of the oscillation circuit.