JPS5951053B2 - Automatic tape speed switching device for magnetic recording and reproducing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic tape speed switching device for a magnetic recording and reproducing apparatus capable of recording and reproducing at least two different magnetic tape speeds.

Hereinafter, to simplify the explanation, a video tape recorder (hereinafter referred to as VTR) will be used as the magnetic recording and reproducing device, and the running speed of the magnetic tape will be of two types: high speed VH and low speed VL, and VH, 2VL. shall be.

In a VTR capable of recording and reproducing at two types of tape speeds, VH and VL, during normal use, it is required to perform playback at the same tape speed as the tape speed at the time of recording.

In the past, the tape speed was written on the reel, cassette half, or case of the recorded magnetic tape, and when playing back, the operator read this and manually switched the playback tape speed. However, such manual switching operations are not only troublesome, but if the tape speed is not listed above, play back at one of the tape speeds and check the image or audio, then switch back to the same tape speed. or switch to another tape speed.
Furthermore, when recording is performed on a single magnetic tape at different tape speeds, it is necessary to perform a switching operation each time. - For this reason, there is a need for an automatic tape speed switching device that automatically switches the tape speed during playback to the tape speed during recording.

As a conventional automatic tape speed switching device, one has been proposed that automatically switches the tape speed by counting the frequency of a control pulse signal recorded on a control track on a videotape, but the circuit configuration is complicated. Furthermore, since a control track and a control head are indispensable, this becomes an obstacle to simplifying the configuration of the VTR.

The present invention has been made in view of the above circumstances, and has a relatively simple circuit configuration, and moreover, detects the tape speed during recording without using a control track, and automatically adjusts the tape speed during playback. An object of the present invention is to provide an automatic tape speed switching device for a magnetic recording/reproducing device.

To achieve this objective, the automatic tape speed switching device for a magnetic recording/reproducing apparatus according to the present invention switches between at least two types of tape speeds to record and reproduce audio signals. In a magnetic recording and reproducing apparatus, means for modulating a first frequency signal with a second frequency signal to form a discrimination signal during high-speed recording, adding the discrimination signal to an audio signal and magnetically recording it on an audio track; , comprising means for detecting the discrimination signal from the playback signal of the audio track during playback, and means for automatically switching the tape speed to a tape speed according to the detected discrimination signal, the discrimination being recorded on the audio track during high-speed recording. The tape speed is automatically switched during playback based on the signal.

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block circuit diagram schematically showing a VTR equipped with an automatic tape speed switching device according to the present embodiment.

This FIG. 1 shows a two-head type VTR, in which rotating magnetic heads 2 and 3 that scan the magnetic tape 1 diagonally are
It is rotationally driven by a motor 4. The audio head 5 and the control head 6 are arranged near both ends of the magnetic tape 1 in the width direction. The capstan 7 and the pinch roller 8 hold the magnetic tape 1 under pressure, and when the capstan 7' is rotationally driven by the motor 9, the magnetic tape 1 runs in the direction of arrow X, for example. The rotation detector 10 generates a periodic signal having a frequency n times the rotation speed of the motor 9 (n is an integer), and is also called a frequency generator. from the rotation detector 10 which is this frequency generator. The periodic signal is converted into a pulse signal by the waveform shaping circuit 11 and becomes a rotation detection pulse signal.

Capstan servo is performed by controlling the rotational phase and rotational speed of the capstan drive motor 9 based on this rotation detection pulse signal. Ru. Various configurations of this capstan servo system are already known, so to briefly explain only the outline, the rotation detection pulse from the waveform shaping circuit 11 is first transmitted to the phase system servo circuit 1.
2, and a phase comparison with a reference pulse is performed.
At this time, the frequency of the rotation detection pulse is lowered by a frequency downgrader or the like, and further converted into a trapezoidal wave or the like, and then the slope portion of this trapezoidal wave is sampled and held using the reference pulse. As this reference pulse, for example, a vertical synchronizing signal of a video signal is used during recording, and a pulse signal from a pulse generator, for example, is used during reproduction. Furthermore, the output from this phase-based servo circuit 12 is sent to a speed-based servo circuit 13. This speed system servo circuit 13 is equipped with a trapezoidal wave generating circuit, and has a switchable tape speed VH.
, V, a changeover switch 14 for changing the inclination angle of the trapezoidal wave generating circuit according to V, and capacitors 15H, 1
5L is connected. The trapezoidal wave signal obtained here is
The signal is sampled and held by a sampling pulse corresponding to the rotation detection pulse from the waveform shaping circuit 11, and becomes a control signal. This control signal is sent to the capstan drive motor 9 via a motor drive circuit 16 which is an amplifier. The changeover switches 17, 18, and 19 are for changing recording/reproducing operations.
is for the video signal, the changeover switch 18 is for the control pulse signal, and the changeover switch 19 is for the audio signal.

First, to explain the video signal system and control pulse signal system, during recording, the changeover switches 17 and 18 are
is switched to the terminal R (RecOrd) side.

At this time, the video signal to be recorded is supplied to the input terminal 20 and then supplied to the terminal H or L of the changeover switch 22 via the amplifier 21H or 21L. This selector switch 22 is used to switch according to the tape speed during recording, and when high speed VH is selected, terminal H (High speed) is selected.
ed) side to change the output from the amplifier 21H to the low-speed V
When it is L, it is switched to the terminal L (LOWspeed) side, and the output from the amplifier 21L is supplied to the terminal R of the next changeover switch 17. Since the changeover switch 17 is switched to the terminal R side, the signal from the amplifier 21H or 21L is sent to the rotary heads 2 and 3 and recorded on the magnetic tape 1 obliquely. Above input terminal 2
A part of the video signal supplied to the vertical synchronization separation circuit 23 is sent to the vertical synchronization separation circuit 23 and becomes a control pulse. This control pulse is amplified by the amplifier 24, sent to the control head 6 via the terminal R of the changeover switch 18, and recorded on the control track of the magnetic tape 1. During playback, the changeover switches 17 and 18 are switched to the terminal P (playback) side. The reproduced video signals from the rotating magnetic heads 2 and 3 are transferred to the selector switch 17.
The signal is sent to the regenerative amplifier 25H or 25L through the terminal P of the . The automatic changeover switch 26, as described later,
It automatically switches to terminal H or terminal L according to the tape speed detection signal, and when switching to the terminal H side, the output from the amplifier 25H is output, and when switching to the terminal L side, the output from the amplifier 25L is output. is supplied to the output terminal 28 via the muting circuit 27. The muting circuit 27 is for preventing the generation of noise when switching tape speeds, as will be described later. On the other hand, the control pulse signal obtained from the control head 6 is amplified by the amplifier 29 via the changeover switch 18.
Although not shown, the control pulses from the amplifier 29 are normally used in the servo system of the motor 4 that rotationally drives the rotating magnetic heads 2 and 3. It may also be used in a capstan servo system as described above.
Next, the audio signal system will be explained along with the tape speed and automatic switching device.

During recording, the selector switch 19 is switched to the terminal R side, and the audio signal supplied to the input terminal 30 is
After passing through a low-pass filter 31 and adding a tape speed determination signal in an additional circuit 32, the signal is sent to the audio head 5 via an equalizer amplifier 33 and recorded on the audio track of the magnetic tape 1.

The low-pass filter 31 is mainly used to limit audio signals to a magnetically recordable frequency band. In reality, the higher the tape speed, the higher the maximum recordable frequency value, so when the tape speed is high VH, the recordable frequency band is wider than when the tape speed is low V1, and this widened part The above-mentioned tape speed discrimination signal can be arranged. For example, when the cutoff frequency of the low-pass filter 31 is set to 7 KHz, the frequency of the discrimination signal is set higher than this, for example, 10 KHz.

Furthermore, in order to prevent malfunctions in detection of the discrimination signal during reproduction, the 10 KHz single signal is modulated with another constant frequency, for example, a 1 KHz sine wave signal, and this is used as the discrimination signal. Specifically, the output signal of the 10 KHz oscillator 34 and the output signal of the 1 KHz oscillator 35 are sent to the AM modulator 36, where they are AM-modulated and used as a discrimination signal. Hatakeru = Futawasa ↓ degrees.

, , respectively, and the terminal L may be left open in this case. The output from this changeover switch 37 is sent to an additional circuit 32, and the discrimination signal is added to the audio signal only when recording at high speed VH. Next, during reproduction, the changeover switch 19 is switched to the terminal P side, and the reproduced audio signal from the audio head 5 is sent to the reproduction equalizer amplifier 39.

The output of this reproduction equalizer amplifier 39 is directly connected to the terminal L of the automatic changeover switch 40 or to the low pass filter 4.
1 to the terminal H of the automatic changeover switch 40. This low-pass filter 41 is similar to the above-mentioned low-pass filter 31.
For example, only frequency components of 7 kHz or less are passed. The audio signal from the automatic changeover switch 40 is supplied to an audio signal output terminal 44 via a line amplifier 42 and a muting circuit 43. By the way, the tape speed determination signal includes a carrier wave in the audio signal as a 10 KHz (7) AM modulation signal only when the tape speed during recording is a high VH. When the magnetic tape 1 is reproduced at a low speed V, (=1/2 VH), the carrier wave becomes a 5 KHz (7) AM modulation signal.

For this reason, the output signal from the reproduction equalizer amplifier 39 is sent to the terminal L of the automatic changeover switch 46 through a bandpass filter 45 whose passband is around 5 KHz. When playing back on high-speed VH, the carrier wave is 10KH.
Since the z(7) AM modulation signal is obtained, the output signal from the reproduction equalizer amplifier 39 is sent to the terminal H of the automatic changeover switch 46 through a high-pass filter 47 whose passband is around 10 KHz or higher. The tape speed determination signal obtained from the automatic changeover switch 46 is processed by the AM demodulation circuit 48, in which the carrier wave component of 10KHz or 5KHz is removed, and the carrier wave component of the above-mentioned 10KHz or 5KHz is removed, and the signal is converted to another constant frequency of 1KHz or 5KHz.
It becomes a sine wave signal of 00 pressure. This sine wave signal is
11? , ~1KHz bandpass filter 49
The noise component is removed by passing the signal through the detection and integration circuit 50.
Detect and integrate to obtain a DC signal. This DC signal is sent to an amplifier 52 via a delay circuit 51 to prevent malfunction.
After amplifying the signal, the signal is sent to an output circuit 53, such as a flip-flop, which has two stable states. This output circuit 53 outputs a signal from the amplifier 52 when there is a signal from the amplifier 52, that is, when the tape speed determination signal is included in the reproduced audio signal.
An output is generated from the H side output terminal, and when there is no signal from the amplifier 52, an output is generated from the L side output terminal. The output from the H side output terminal of the output terminal 53 is sent to the automatic changeover switches 14, 26, 40 and 46, and these switches are switched to the terminal H side. Here, if the above discrimination signal is detected while the automatic changeover switch 46 is switched to the terminal L side, the automatic changeover switch 46 is switched from the terminal L side to the terminal L side by the output from the H side terminal of the output circuit 53. At this time, the DC signal from the detection and integration circuit 50 is momentarily interrupted, but since the delay circuit 51 maintains the output, adverse effects such as chattering can be prevented. In this sense, the delay circuit 51 is also a hold circuit. Moreover, the H side output and the L side output of the output circuit 53 are the same. The signals are sent to indicator lamps 54H and 54L, respectively, to display the tape speed during recording. Furthermore, the above H side output and L
The side outputs are sent to monomulti 56 via diodes 55H and 55L, respectively. The output from this monomulti 56 is shown above. Muting circuits 27 and 43
The muting circuits 27 and 43 temporarily interrupt the reproduction signal. This is the automatic changeover switch 14
, 26, 40, and 46 to eliminate noise that occurs when switching operations. The above explanation was mainly for the case where the tape speed during recording was high VH and the reproduced audio signal contained a modulated signal with a carrier wave of 10 KHz or 5 KHz. However, if the tape speed during recording was low speed In the case of V, the above-mentioned modulation signal is not included, so no DC signal is obtained from the detection and integration circuit 50, and the output circuit 53 produces an output only from the L side output terminal. , 40 and 46 are all switched to the terminal L side.

Specifically, for example, each automatic changeover switch 14,
26, 40, and 46 are used as self-resetting type switches, so that they switch to the terminal H side only when the H side output of the output circuit 53 is supplied, and always self-return to the terminal L side in other states. All you have to do is do it. Of course, a bistable operation type in which the L side output of the output circuit 53 switches to the L side terminal may also be used. Note that when a magnetic tape recorded at low speed VL is reproduced at low speed V, a 5 KHz signal unrelated to the tape speed discrimination signal may be included in the reproduced audio signal.

However, this 5KHz signal is 500Hz to 1KHz
It is very rare that the signal is modulated by a sine wave signal, and in most cases no output is obtained from the bandpass filter 49, and no H-side output from the output circuit 53 is generated.
Furthermore, even if a 5KHz signal modulated by a 5001-b-1KHz sine wave signal is included in the reproduced audio signal, since the duration is generally extremely short, it is removed by the delay circuit 51 and the output circuit The H side output of 53 is not generated. Therefore, according to the embodiment of the present invention, the tape speed discrimination signal during recording can be detected regardless of whether the tape speed during playback is high VH or low speed VL, and this tape speed discrimination signal can be used. Accordingly, the playback tape speed can be automatically switched to the recording tape speed.

Furthermore, since the tape speed determination signal is added to the audio signal, no control track is required. Furthermore, a constant frequency (
10KHz) to another constant frequency (1KHz
), this greatly reduces malfunctions caused by signals contained in the original audio signal or other noise signals.

Further, since the muting circuits 27 and 43 are used, noise during automatic tape speed switching can be eliminated, and the viewing experience is also good. Note that the present invention is not limited to the above-mentioned embodiments. For example, even when recording and reproducing at three or more different tape speeds, it is possible to distinguish between the carrier wave frequency and the modulation signal frequency at any playback tape speed. By making the difference as desired, it is possible to determine the tape speed at the time of recording.

Claims (1)

[Claims] 1. In a magnetic recording and reproducing device that records and reproduces audio signals by switching between at least two types of tape speeds,
means for modulating a first frequency signal with a second frequency signal during high-speed recording to form a discrimination signal, adding the discrimination signal to an audio signal and magnetically recording it on an audio track; and a means for magnetically recording the discrimination signal on an audio track during reproduction; means for detecting the discrimination signal from the reproduced signal, and means for automatically switching the tape speed according to the detected discrimination signal,
1. An automatic tape speed switching device for a magnetic recording/playback device, characterized in that the tape speed is automatically switched during playback based on a discrimination signal recorded on an audio track during high-speed recording.