JPS6057152B2 - magnetic tape playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape reproducing apparatus for reproducing a magnetic tape on which audio information signals and signals such as encoded characters, images, or numerical information are recorded.

2. Description of the Related Art Conventionally, a VTR (video tape recorder) has been used as a magnetic tape reproducing device that simultaneously reproduces audio information and information such as images.

However, since VTRs require images similar to those of television broadcasting, the equipment has to be complicated, large, and expensive. Therefore, in order to reproduce text or simple graphics on an image display device at the same time as audio, which does not require high-definition images such as VTR images, we have developed a magnetic tape playback device that uses general-purpose audio magnetic tape. is proposed. This magnetic tape playback device records an audio information signal on the first channel of an audio magnetic tape having two channels, and records a signal encoded with information such as characters on the other second channel of the magnetic tape. By reproducing this magnetic tape, text and the like are reproduced on an image display device at the same time as audio.
FIG. 1 shows a conventional block diagram of this type of magnetic tape reproducing apparatus.

In FIG. 1, 1 is a magnetic tape player, 2 is a first amplifier for amplifying audio information signals, 3 is a speaker, 4 is a second amplifier for amplifying information signals such as characters, and 5 is a first amplifier for amplifying information signals such as text. A signal processing circuit, 6 an image display device, 7 a DC power supply circuit,
8 is a switch. Reproduction of the audio information signal of the first channel is performed by the first amplifier 2 and the speaker 3.

On the other hand, the information signal such as characters on the second channel is amplified by the second amplifier 4, and then converted by the signal processing circuit 5 into a signal suitable for displaying on the image display device 6. This is what is displayed. Switch 8 in FIG. 1 is used for the following purposes.

That is, as can be seen from FIG. 1, this magnetic tape reproducing device is equipped with a first amplifier 2 for reproducing audio information signals and a speaker 3, so that it can reproduce the aforementioned audio information signals and information such as encoded characters. It is possible to play not only magnetic tapes on which both signals are recorded (hereinafter referred to as audio and text information magnetic tapes), but also ordinary magnetic tapes on which audio information signals are recorded on both channels (hereinafter referred to as audio magnetic tapes). It is. However, in the case of reproducing this audio magnetic tape, the signal processing circuit 5 is not necessary, and moreover,
Since the signal processing circuit 5 is often composed of a microcomputer or the like and consumes a large amount of power, the switch 8 is used to cut off the DC power supply voltage applied to the signal processing circuit 5 to eliminate unnecessary power consumption. It is. However, this conventional magnetic tape reproducing device had the following drawbacks.

In other words, the switch 8 is set depending on the magnetic tape used.
The operability was very poor because the user had to switch between them one by one. Furthermore, when reproducing the audio magnetic tape, it was often the case that the user forgot to turn off the switch 8, resulting in wasted power consumption.
An object of the present invention is to eliminate the drawbacks of the conventional magnetic tape reproducing apparatus described above, and to provide a magnetic tape reproducing apparatus that automatically turns on or off a switch for applying a DC power supply voltage to a signal processing circuit depending on the magnetic tape used. There is a particular thing.

The present invention provides a second signal detection circuit such that an output is obtained when the encoded text information signal in the second channel of the audio and text information magnetic tape is available at the output of the second amplifier. It is connected to an amplifier circuit, and uses the output of the signal detection circuit to control a switching circuit that applies a DC power supply voltage to a signal processing circuit.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a first embodiment of the invention. In the figure, 9 is a signal detection circuit, 10 is a switching circuit, and the switching circuit 10 is connected to a drive circuit 11 and a relay 12.
Consisting of Other symbols are the same as in FIG. 1.
Generally, when recording character information etc. on a magnetic tape by encoding it with the codes ゜゜0゛ and ゜"1゛, the code 6601 or '6r5 is used as an FS (Frequency Shift) signal that corresponds to a signal of a specific frequency. A recording method is used.

Therefore, when the audio and text information magnetic tape is reproduced, the second amplifier 4 is outputted with a signal of the above-mentioned specific frequency. Therefore, by configuring the signal detection circuit 9 so that an output is obtained only when a signal of this specific frequency is input, the output of the signal detection circuit 9 can also be made A drive circuit 11 drives a relay 12 and applies a DC power supply voltage to a signal processing circuit 5. In the embodiment shown in FIG. 2, among the audio information signals during playback of the audio magnetic tape, a signal having the same frequency as the above-mentioned specific frequency that happens to be output to the signal detection circuit 9 is detected as a signal. If the signal is input to the circuit 9, the relay 12 may operate in the same manner as when playing back audio and text information magnetic tape.

Therefore, although not shown in the figure, the output of the signal detection circuit 9 and the output delayed by a certain period of time are ANDed.
In addition to the above circuit, if the AND output of these two outputs is applied to the drive circuit 11, when the audio magnetic tape is reproduced, a specific frequency that provides an output to the signal detection circuit 9 appears at the same time interval as the delay time. Since the probability of this happening is extremely low, it is possible to eliminate malfunctions of the relay 12. Furthermore, by connecting an integrating circuit with a sufficiently large time constant to the output of the signal detection circuit 9 or the drive circuit 11, the signal occasionally output from the signal detection circuit 9 during audio magnetic tape playback can be removed, and the malfunction of the relay 12 can be prevented. It is possible to prevent this. FIG. 3 shows a second embodiment of the invention.
In FIG. 3, 13 is a transistor, and other symbols are the same as in FIG. 1. In this second embodiment, a transistor 13 is used as a switch instead of the relay used in the first embodiment, and when an output is obtained in the signal detection circuit 9, that is, a voice or a character is detected. Only when reproducing an information magnetic tape, the transistor 13 is driven to a saturated state, and a DC power supply voltage is applied to the signal processing circuit 5. FIG. 4 shows a third embodiment of the invention.

14 is a thyristor, and the other symbols are the same as in FIG. 1. In this third embodiment, while the first and second embodiments require that the signal detection circuit 9 be provided with an output during the period when the audio and text information magnetic tape is being reproduced, Audio and text information A signal at the start portion of the second channel on which text information of the magnetic tape is recorded is detected by a signal detection circuit 9 and inputted to the gate of a thyristor 14 by a drive circuit 11. As is well known, the thyristor 14 has an input applied to its gate,
Once conductive, it continues to be conductive even if the input to the gate is removed, so there is no need for an output to drive the switch during the entire magnetic tape playback period as in the first or second embodiment. The signal at the start portion of the magnetic tape in this third embodiment is generally such that when character information, etc. is encoded and recorded on the magnetic tape, the start portion includes character information etc. in which the recorded content is encoded. In order to indicate that the signal is a signal, several signals made with a specific combination of codes ゜"0゛ and ゜゜1゛ are repeatedly recorded, so this signal may be used,
Alternatively, several signals that continue for a short time may be repeatedly recorded at certain time intervals and used as the start signal. Then, the output of the signal detection circuit 9, which outputs an output only when these signals are input, is connected to the output of the signal detection circuit 9, and this output is connected to the time interval of repetition of the start signal recorded on the magnetic tape. If one or several outputs delayed by the same amount of time are added to the AND circuit, and the AND output is applied to the gate of the thyristor 14 by the drive circuit 11, the thyristor 14 is activated when playing back a magnetic audio tape. 14 malfunctions can be avoided. In addition, in Fig. 4, thyristor 1
4 is used, but it goes without saying that the same function can be obtained by using two transistors connected to a thyristor. According to the present invention, the DC power supply voltage applied to the signal processing circuit is automatically turned off when audio magnetic tape is reproduced, and the DC power supply voltage is automatically turned on to the signal processing circuit only when audio and text information magnetic tape is reproduced. This significantly improves operability.

Additionally, unnecessary power consumption due to forgetting to turn off the manual switch in the conventional case can be eliminated.

[Brief explanation of the drawing]

Fig. 1 shows a conventional magnetic tape playback device; Fig. 2;
FIGS. 3 and 4 are block diagrams showing embodiments of the present invention, respectively. 1: Magnetic tape player, 2: First amplifier, 4: Second amplifier, 5: Signal processing circuit, 9: Signal detection circuit, 10: Switching circuit.

Claims (1)

[Claims] 1. The output of the first channel of a magnetic tape player having two playback channels is input to a first amplifier, the output of this first amplifier is connected to an electro-acoustic transducer, such as a speaker, and the output of the first channel is input to a second amplifier. The output of the channel is input to a second amplifier, the output of this second amplifier is input to a signal processing circuit, the output of this signal processing circuit is connected to an image display device, and the output of this second amplifier is input to a signal processing circuit, the output of which is connected to an image display device, and the output of this second amplifier is input to a signal processing circuit, and the output of this signal processing circuit is connected to an image display device, and the output of this second amplifier is input to a signal processing circuit. is applied to each of the above circuits, a signal detection circuit whose input is the output of the second amplifier is connected, and a switching circuit controlled by the output of the signal detection circuit is connected to the above signal processing circuit. A magnetic tape playback device, characterized in that the switching circuit is connected between a circuit and a DC power supply voltage applied to the signal processing circuit, and closes the switching circuit only when an output is obtained in the signal detection circuit.