JPS61253671A - Control signal recording and detecting circuit - Google Patents

Abstract

PURPOSE:To simplify an adjusting process, and to decrease the number of parts by using in common an oscillation source of a scheduled frequency signal at the time of recording, and a reference oscillation source for taking the conformity to the scheduled frequency signal at the time of a detection, by the same oscillation source. CONSTITUTION:A voltage control oscillator 11 executes stably an oscillation by a free-running frequency which is set by a free-running frequency setting circuit 15, and its output is amplified by an amplifier 17 through a low-pass filter 16, brought to a bias processing by a bias circuit 18, and written as a control signal to a recording medium from a recording head 19. On the other hand, a frequency signal component which has been caught by a reproducing head 20 is applied to an input terminal Ti of a tone decoder 10 from a switching circuit 13 through an amplifier 21, and when a phase of the output of the voltage control oscillator 11 has been matched to a phase of this component by the first comparator 12, and a signal to be detected and an oscillation frequency of the voltage control oscillator 11 have been matched in a prescribed band width by the second comparator 22, a detecting signal is generated. This detecting signal is fetched to the outside from an output terminal To through a low-pass filter 23 and an amplifier 24.

Description

[Detailed Description of the Invention] <Industrial Application Fields> The present invention is capable of recording control signals based on a predetermined frequency on a recording medium such as a magnetic recording tape, or conversely, recording a control signal based on a predetermined frequency from the recording medium. This invention relates to improvements in control signal recording and detection circuits required when detecting control signals.

<Prior Art> Recently, applied devices that use recording media such as magnetic recording tapes as analog or digital external non-volatile recording media, such as audio tape recorders or players, personal computers, answering machines, etc. , the market is increasingly expanding.

Under these circumstances, it is not only necessary to record only the necessary information on the recording medium, but also to record cue signals for music selection, computer programs, etc.
It has become necessary to superimpose various control signals such as tape end signals and message separation signals for answering machines.

In such a case, the control signal needs to be recorded so as not to interfere with the original information signal, but at the same time, during playback, it must be detected in a clearly differentiated state without being confused by the group of information signals. It must be.

Conventionally, the recording methods for this type of control signal generally include those that record a continuous signal of a scheduled (usually constant) frequency as a control signal, and those that encode a scheduled frequency intermittently and record this as a control signal. etc., but in any case,
At a minimum, the required circuit components include a recording oscillation source that oscillates at the scheduled frequency, and a source that matches the frequency component of the scheduled frequency from among the various signal components read from the recording medium during playback. It is a reference oscillation source that oscillates at the same predetermined frequency for detection.

<Problems to be Solved by the Invention> In all conventional control signal recording and detection circuits composed of the circuit elements described above, the recording system and the detection system are considered to be completely separate and independent circuits. That is, in accordance with the recent trend, when using each integrated circuit in this type of circuit system, independent integrated circuit modules have been used.

Therefore, the scheduled frequency oscillation source for recording and the reference frequency oscillation source for comparison at the time of detection are also constituted by separate oscillators, and this is rather easier in terms of design and handling.

However, doing so required careful adjustment to match the oscillation frequencies of the recording and detection oscillation sources with each other immediately before shipping the product, which was extremely troublesome. .

In addition, even if accurate adjustment is made, unless both oscillators have exactly the same change characteristics due to aging or temperature changes, even if the change width of each oscillator's characteristics is small, the sum of the change widths of both oscillators In some cases, this amounted to an unacceptable level.

In order to avoid the above-mentioned troubles and to minimize the negative effects of environmental characteristics such as aging and temperature changes, the only way to do this is to make the oscillation sources used individually highly stable. , which is generally almost impossible to achieve without using an extremely expensive crystal oscillator.

The present invention has been made in view of these conventional circumstances, and it is an object of the present invention to provide a control signal recording and detection circuit that is inexpensive and capable of reliably recording and detecting control signals with almost no adjustment. .

Means for Solving the Problems> In order to achieve the above object, the present invention records a control signal representing a specific meaning on a recording medium using a predetermined frequency, and at the same time records the control signal on the recording medium. A control signal recording detection circuit detects, as a control signal component, a frequency component that matches the scheduled frequency from among various signal components being recorded, the circuit comprising: an oscillation source of the scheduled frequency signal at the time of recording;
Provided is a control signal recording and detection circuit characterized in that the same oscillation source is used as a reference oscillation source for matching the scheduled frequency signal at the time of the detection.

<Function> In the present invention, a single oscillation source functions as an oscillation source at both the time of recording and the time of detection of a control signal.

Therefore, it is theoretically possible that there is a difference in relative oscillation frequency between the oscillation sources used during recording and during detection, and therefore it is not possible to accurately detect the control signal without making precise adjustments. It is sufficient for a zero oscillator that can oscillate stably to some extent, and it is even conceivable that no adjustment is required.

Also, for the same reason, the oscillation frequency of the oscillation source used does not need to be accurate in absolute value, and there is no problem even if it deviates slightly from the design value, so expensive crystal oscillators and circuit components with good environmental coefficients etc. This can be omitted, resulting in a fairly inexpensive oscillation source.

EXAMPLE A preferred embodiment of the present invention, shown in FIG. A voltage controlled oscillator (VCO) 1 used and also commonly included in this type of tone decoder 10
1 is used as a common oscillation source during control signal recording and detection.

Specifically, this type of frequency signal detection integrated circuit or tone decoder 10 is model number LM5B sold by Nihon Signetics Co., Ltd. There is a module.

In FIG. 1 and FIG. 2, the signal path indicated by a solid line is the signal path that is valid at that time.
The signal path indicated by the virtual line is a signal path that is disabled or unnecessary at that time. FIG. 1 shows the control signal at the time of recording, and FIG. 2 shows the time of detection.

First, the case of recording control signals on a magnetic recording tape will be explained with reference to FIG.

The voltage controlled oscillator 11 built into the tone decoder IO used is under feedback control by a phase locked loop. That is, the voltage controlled oscillator 11
The output oscillation frequency is determined by the built-in phase comparator (φDFT) 12.
The output of the phase comparator 12 is applied to one input of the voltage controlled oscillator 11 via a low pass filter (LPF) 14, which is simply shown as an external capacitor C2 in the figure.
The control voltage is supplied to the

In this case, from the regenerative radar 20 through the regenerative amplifier 21,
Since the signal path leading to the signal input terminal Ti of the tone decoder 10 is cut off by the switch circuit 13 during recording, the voltage controlled oscillator 11 is set by the external free-running frequency setting circuit 15. It oscillates fairly stably at the free running frequency.

In general, this free-running frequency setting circuit 15 can be configured with a simple time constant circuit, etc., including a resistor r1 and a capacitor C1, as shown in the figure. Furthermore, the switch circuit 13 may be of an attenuator type that applies sufficient resistance attenuation to the input signal, rather than simply turning off the signal path.

However, in such a tone decoder 10,
Among the terminals to which the free-running frequency setting circuit 15 is externally connected, the output of the voltage-controlled oscillator 11 appears as it is at one terminal ↑S, so the oscillation output is extracted from there and recorded as a control signal on a recording medium. Used as a frequency for personal use.

In other words, when the output of the voltage controlled oscillator 11 is a rectangular wave or the like, an appropriate low pass filter 16 is used to prevent the harmonics from beating the recording bias frequency.
After this is amplified appropriately by the recording amplifier 17, it is normally
A bias process required for this type of magnetic recording is performed, and a control signal is written from the recording head 18 onto a recording medium such as a magnetic tape (not shown).

In this way, when detecting the control signal written on the recording medium, the signal path shown by the solid line in FIG. 2 is used.

Some frequency signal components captured by the reproducing head 20 are passed through a reproducing amplifier 21 as appropriate, and then sent to a switch circuit 13.
to the detected signal input terminal Ti of the tone decoder 10.

From this detected signal terminal Ti, not only the value input of the phase comparator 12 mentioned above but also the second phase comparator (φ[l
ET#2) A signal line also extends to 22's solo power.

If the signal applied to this input terminal Ti contains a frequency component of the target control signal, the frequency of this component is originally the oscillation frequency of the voltage controlled oscillator 11, so One comparator 12 functions to match the phase of the output of the voltage controlled oscillator 11 with the phase of this component.

On the other hand, the second comparator 22 emits a detection signal when the input detected signal and the oscillation frequency of the voltage controlled oscillator 11 match within a predetermined bandwidth. If the target control signal component is included in the signal applied to the input terminal Ti, the detection signal is output as, for example, a significant voltage value or logic "H+t." Furuta 2
3 or the amplifier 24 to the output terminal To, the purpose of detecting the control signal is achieved.

With the above configuration, since the free-running frequency of the same voltage-controlled oscillator 11 is used for recording and detecting control signals, the free-running frequency of the voltage-controlled oscillator 11 must be strictly adjusted to a constant value. There is no problem with the tolerance of each product regarding the resistor rl and capacitor C1 in the free-running frequency setting circuit 15.

In addition, in such a voltage controlled oscillator 11, temperature changes and changes over time are generally only a few percent at most.
It can be placed well within the band of a tone decoder.

In the above embodiment, dedicated heads are used for the recording head 19 and the reproducing head 20, but as is commonly done in this type of magnetic recording technology, an appropriate switching circuit may be used. By adopting this, a so-called recording/reproducing head type may be used.

Accordingly, it is also possible to share the recording amplifier 17 and the reproducing amplifier 21 by switching the use of a single amplifier.

Furthermore, the present invention can be effectively applied to a case where the control signal is a continuous wave of the oscillation source frequency as in the above embodiment, but is encoded by appropriately intermittent the oscillation source frequency. For example, a configuration in which an encoder or a modulator is inserted in the path from the output of the voltage controlled oscillator 11 to the recording head 19 using known existing technology can be very easily considered.

In such a case, a pulse train corresponding to a signal train whose frequency is synchronously intermittent is obtained at the output terminal TO of the tone decoder 10.

An even more fundamental problem is that, in addition to the above-mentioned magnetic recording tape, the recording medium can be any other medium, such as a magnetic disk, as long as it is capable of writing frequency signals.

<Effects of the Invention> In the present invention, since the same oscillation source is used for recording and detecting control signals, it is not necessary to match relative frequencies as when using individual oscillation sources. do not have.

There is also no need to strictly match the oscillation frequency of the oscillation source to a particular value in absolute value.

Therefore, the adjustment process is significantly simplified, and of course, the number of parts shared by the recording section and the detection section can be reliably reduced. Therefore, failure probability and the like can also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram illustrating the signal flow during recording in a preferred embodiment of the control signal recording/detection circuit of the present invention, and FIG. 2 is a schematic diagram illustrating the signal flow during detection in the same embodiment. FIG. 2 is a schematic configuration diagram for explanation. In the figure, lO is a tone decoder, 11 is a voltage controlled oscillator, 12.22 is a phase comparator, 13 is a switch circuit, 15
1 is a free-running frequency setting circuit, 19 is a recording head, and 20 is a reproducing head.

Claims (1)

[Claims] While a control signal representing a specific meaning is recorded on a recording medium using a predetermined frequency, the predetermined frequency is selected from among various signal components recorded on the recording medium. A control signal recording detection circuit that detects a frequency component that matches as a control signal component; an oscillation source of the scheduled frequency signal at the time of recording;
A control signal recording and detection circuit characterized in that the same oscillation source is used as a reference oscillation source for matching the scheduled frequency signal at the time of the detection.