JPS59117747A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the program search of an unrecorded part by reproducing a program search signal applied with phase-modulation to its control signal so as to operate the 1st or 2nd switching circuit. CONSTITUTION:A DC converting output level of an integration circuit comprising resistors R5, R6 and a capacitor C2 or the like is changed into a low level via a transistor (TR) Q1 being turned on during the period in response to the duty value in response to a reproducing signal of a program search signal in which the control signal of 50% duty cycle is equal phase-modulated by 75% duty cycle. This DC converting output is applied to the 1st detecting circuit 10 via a switch SW, TRQ11, Q12 are turned on, and a program search detecting output is generated. On the other hand, when a switch SW is changed over, the TRQ1 remains off at the unrecorded part, TRQ13, Q14 of the 2nd detecting circuit 11 are turned off, a TRQ15 is turned on, the program search detecting output of the unrecorded part is generated to attain the program search of the unrecorded part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic recording/reproducing device with an improved cueing signal detection circuit.

[Technical background of the invention]

2. Description of the Related Art In a video tape recorder (hereinafter referred to as a VTR), a so-called cue position detection circuit is operated to detect a tape recording start position. As the cue position information, duty information of control pulses recorded on the control track of the tape is used.

For example, the control pulse is approximately 10 minutes from the start of recording.
For a second, the pulse duty is phase modulated to 75% (high level) and recorded, and thereafter the pulse duty is 50%.
recorded.

Therefore, in order to find the recording start position, the tape is fed at high speed, and at this time, the control pulse is introduced into the start position detection circuit, and the position at which the pulse duty is 75% is detected.

FIG. 1 shows a conventional cue position detection circuit, in which a reproduction control pulse (CTL) f'j: is input to the base of a transistor Q1 via a capacitor CI and resistors R1 and R2. Diode DI is for setting the reference level.
Resistor R3 is for base bias. transistor Q
A control pulse whose waveform has been shaped is obtained at the collector of No. 1, and is input to an integrating circuit including a resistor R5 and a capacitor c2, and is converted into a direct current. Resistor R4 is a load resistance. The DC output of the integrator circuit is applied to transistor Q2, which is base biased by resistor R6. The DC level applied to this base is 1 and changes depending on the pulse duty of the control pulse of 75% and 50%. Therefore, the transistor Q2 is set to be off when the pulse duty is 5° and on when the pulse duty is 75% by selecting the divided voltages of the resistors R7 and R8 applied to its collector. The output from collector resistor R9 of transistor Q2 is supplied to the base of transistor Q3 via resistor RIO.

When transistor Q2 is turned off, transistor Q3
When transistor Q2 is turned on, transistor Q3 is also turned on, and a low level detection output is obtained when transistor Q2 is turned on. In this way, the detection signal (A) is at a high level when the pulse duty of the control pulse is 50% and is at a low level when it is 75%, allowing the detection of the recording start position of the tape. This detection signal (A) is introduced into a system control device in a VTR, for example, and
Used as input information for device control.

[Problems with background technology]

According to the conventional cue position detection circuit described above, it is possible to detect the recording start position on the tape, but it is not possible to detect the non-recorded portion.

Since there is no control pulse in the non-recorded area, the capacitor C2 is filled through the resistors R4 and R5, and the transistors Q21 and Q3 are turned on, making it impossible to distinguish between the normal recording position and the normal recording position. However, depending on the magnetic tape, signals are not necessarily recorded on all of the tape, and some are recorded only halfway. If an attempt is made to record another program on the unrecorded portion of such a tape, it is impossible to find the position of the unrecorded portion using the cue detection circuit.

[Purpose of the invention]

This invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a magnetic recording/reproducing apparatus having a retrieval position detection circuit capable of detecting even the unrecorded portion of a signal.

[Summary of the invention]

In Jin's invention, as shown in FIGS. 2 and 3, the performance of the VTR function is improved by providing a second switching circuit 11 for detecting a non-recorded portion.

[Example of Gangugo]

Embodiments of Hanamei with the following will be described with reference to the drawings. Second
The figure shows one embodiment of this consideration, where capacitor C1
, diode DI, resistors R1 to R6, capacitor C2,
The circuit section formed above the transistor, the waveform shaping section of the pulse control pulse, and the integrating circuit section have the same configuration as the circuit shown in FIG. 1, and therefore are given the same reference numerals and a description thereof will be omitted. - In the case of this invention, the DC conversion output of the integrating circuit including resistors R5, R6 and capacitor C2 is applied to the first switching circuit 10 and the second switching circuit 11. 1st
The switching circuit 10 includes transistors Qll, QI
2. It is composed of resistors R21, R22, and R23, and the on/off operating point of the transistor Qll is at the resistor R22°R2
Selected by 3. When transistor Qll turns on, transistor Q12 also turns on, and transistor Qll turns on.
When l is turned off, transistor Q12 is also turned off.

The second switching circuit 11 includes transistors Q13.
Q14. Consisting of Q15 and resistors R25 to R29,
The on/off operating point of the transistor Q13 is the resistor R27,
It is determined by selecting the power supply voltage division voltage of R26.

When transistor Q13 turns on, transistor Q14
is on and transistor Q15 is off. When transistor Q13 is off, transistor Q14 is off and transistor QZ5 is on.

The output of the integration circuit is connected to the pace of the transistor Qll through the switch section SW2 of the switch circuit SW.
It is input to either one of the bases of transistor Q13. Furthermore, either the collector of the transistor Q12 or the collector of the transistor Q15 is connected to the switch portion S'.
7i11, and the power supply +5 is selected through the resistor 31.
V and is also connected to the detection signal output terminal via a resistor 32.

The switch units 5tVZ and SW2 work together to set either the first or second switching circuit 10.11 to the detection state.

One embodiment of this invention is constructed as described above, and when cueing the recording start portion, the switch circuit SW switches the first
The switching circuit 10 is put into operation. The first switching circuit 10 detects the M(th f tq part (duty 75%)) of the control pulse signal.
When a reproduction signal (heading signal) is input to the phase modulation section, the base potential of the transistor Qll decreases, the transistors Qll and Ql2 are turned on, and the first detection signal becomes low level.

Next, when obtaining the cue of a non-recorded portion, the switch circuit SW is switched to put the second switching circuit II into the operating state. As long as the regeneration output of the control trunk contains the control pulse signal, the transistor Q
Since l is turned on in response to the pulse, capacitor C2 cannot maintain the light adjustment voltage. However, when the unrecorded portion is reproduced, the transistor Q1 remains off and the capacitor C2 remains full, thereby turning off the transistor Q13. Therefore, the transistor QI4 is turned off and the transistor Q15 is turned on.
A detection signal (non-recorded section cue signal) is obtained.

FIG. 3 shows a second embodiment. In this embodiment, the switch circuit SW described above is omitted, and the parts common to the embodiment of FIG. 2 are given the same reference numerals and the explanation thereof will be omitted.

The operating point of the transistor Q11 is set so that it turns on when a control pulse signal with a duty of 75% is input, and turns off when a control pulse signal with a duty of 50% is input. Also, transistor Q
The operating point No. 13 is set so that it turns on when a control pulse signal with a duty of 75% and 50% is input, and turns off when there is no signal. As a result, the detection signal A is transmitted to the phase modulation section (recording start section) of duty 75,
And the low level hits in the unrecorded part.

Therefore, in addition to detecting the recording start part and unrecorded part of a tape, when recording signals on a tape, even if a unrecorded part is created in the continuous shooting part, it is not possible to cue at that part. Possible. Furthermore, even if data is written continuously, if the control pulse is phase-modulated at the point where it is desired to cue and the cue signal is generated, this portion can be detected.

〔Effect of the invention〕

As described above, the present invention can provide a magnetic recording and reproducing apparatus that can also cue up the previously recorded portion of a signal and improve the quality.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional cueing signal detection circuit;
3 and 3 are circuit diagrams each showing an embodiment of the present invention. 10...first switching circuit, 1no...second switching circuit, Ql...transistor, Qll~
Q15...Transistor, R22°R23, R27,
R26...Resistance.

Claims (1)

[Claims] In a magnetic recording/reproducing apparatus which records a cue signal in which a control pulse signal is phase-modulated for a predetermined period of time on a tape during recording, a playback signal of the control pulse signal trunk is added, and in response to the cue signal, a first switching circuit that generates a first detection signal that detects a recording start portion on the tape; and a first switching circuit that generates a first detection signal that detects a recording start portion on the tape; and a first switching circuit that detects a recording start portion on the tape; The second one that detected the recorded part
1. A magnetic recording/reproducing device comprising: a second switching circuit that generates a detection signal.