JPH0245250B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a detection and switching device suitable for use in automatic detection and switching of tape types in tape recorders and the like. Conventional configuration and its problems In recent years, tape recorders, etc., automatically detect the tape type and adjust playback equalizers and
Tape type detection and switching devices have come into widespread use for the purpose of automatically switching recording equalizers, recording bias currents, tape type display devices, and the like. This detects the type of tape based on the presence or absence of a detection hole provided in a cassette half, and FIG. 1 shows a comparison of detection holes in a cassette half that has been implemented in recent years. Normal tape NT has no detection hole, chrome tape CT has one on each side on the outside, metal tape MT has chrome tape CT
There are a total of four detection holes W, one on each side and one on the inside, at the same location. Note that they are provided symmetrically on both sides in case the tape is turned over. A conventional detection switching device will be explained below.
FIG. 2 is a side view of the device for detecting the detection hole, where T is a cassette half and SW is a leaf switch, which are fixed in an appropriate manner. With the above configuration, when the cassette half T has a detection hole, the contact point of the leaf switch SW is closed as shown by the solid line in FIG. 2. If the cassette half T does not have a detection hole, the contact of the leaf switch SW will be open as shown by the broken line. FIG. 3 shows a conventional detection and switching device that switches a light emitting diode (hereinafter referred to as LED) for indicating the tape type, a recording equalizer, a playback equalizer, and a recording bias current by turning on and off the leaf switch SW. 1 is a leaf switch for detecting chrome tape, which is installed in the positional relationship shown in Figure 2 above to detect the presence or absence of a detection hole on the outside of the cassette half, and if there is a detection hole, it turns on. and
If there is no detection hole, it is off. Similarly, 2 is a leaf switch for metal tape detection, and the leaf switch 2 is used to detect the detection hole inside the cassette half.
It is provided as shown in the figure, and if there is a detection hole, it is on, and if there is no detection hole, it is off. One end a of the leaf switch 1 is grounded via a resistor 3, and the other end b
is connected to the first power supply 4. leaf switch 1
One end is also one end of the input side of the first AND circuit 5, one end of the input side of the second AND circuit 6, and
It is connected to one end of the input side of the third AND circuit 8 via the NOT circuit 7 and to the base of the transistor 10 via the buffer circuit 9. Further, one end of the leaf switch 2 is connected to the first power source 4, and the other end is grounded via a resistor 11 and the first end is connected to the first power source 4.
The other end of the input side of AND circuit 5, and NOT circuit 1
2, the other end of the input side of the second AND circuit 6,
and the third AND circuit 8 via the NOT circuit 12
is connected to the other end of the input side. 1st AND
The output side of circuit 5 is buffer circuit 13, 14, 15.
through transistors 16, 17, 18 respectively.
similarly connected to the base of the second AND circuit 6
The output side of the third AND circuit 8 is connected to the bases of transistors 22, 23, 24 through buffer circuits 19, 20, 21, respectively, and the output of the third AND circuit 8 is connected to the bases of transistors 28, 29, 24 through buffer circuits 25, 26, 27, respectively. 30. Note that the above transistors 10, 16, 17, 18, 22, 2
Emitters 3, 24, 28, 29, and 30 are each grounded. 31 is an LED for displaying a metal tape, 32 is an LED for displaying a chrome tape, and 33 is an LED for displaying a normal tape.The anode of each LED is connected to the first power supply 4 through resistors 34, 35, and 36, respectively. The cathodes thereof are connected to the collectors of transistors 17, 23, and 29, respectively. On the other hand, the collector of the transistor 10 is connected to a reproduction equalizer amplifier 37 which takes the reproduction head 38 as an input and outputs it to a reproduction output terminal 39 for switching the equalizer. In addition, the recording signal input terminal 40 is inputted to the + side input terminal and outputted to the recording head 41, while a resistor 42 is arranged between the - side input terminal and the output terminal, and the - side input terminal is connected via the resistor 43. The grounded operational amplifier 44 constitutes a recording equalizer amplifier.
The collector of the transistor 28 is connected to the capacitor 4.
5 and is connected to the negative input terminal of the operational amplifier 44 via a coil 47. The collectors of the transistors 22 and 16 are connected to the negative input terminal of the operational amplifier 44 through a parallel connection of a capacitor 48 and a resistor 49, and a parallel connection of a capacitor 50 and a resistor 51, respectively. The collectors of the transistors 18, 24, and 30 are connected to the base of a transistor 55 via resistors 52, 53, and 54, respectively, the collector of the transistor 55 is connected to a second power supply 56, and a resistor 57 is connected between the base and the collector. is connected, and the emitter supplies voltage to the bias current generating section 58. The bias current generated by the bias current generator 58 is supplied to the recording head 41. The operation of the detection switching device configured as described above follows the logic shown in the table below depending on the state of the detection hole of the cassette half.

[Table] First of all, for the tape type display LED, if the tape is normal, the transistor 29
is on, so the normal tape display
The LED 33 lights up because a forward current flows through the resistor 36, and the chrome tape display LED 33
The metal tape display LED 31 does not light up because the transistors 23 and 17 are off. Similarly, in the case of chrome tape, for chrome tape display
Only the LED 32 lights up, and in the case of metal tape, only the metal tape display LED 31 lights up. On the other hand, regarding playback equalizer switching, since the chrome tape and metal tape use the same equalizer, the transistor 10 is turned on when the chrome tape and metal tape are used, and the playback equalizer is switched. Furthermore, the gain of the recording equalizer amplification section is generally set in the order of normal < chrome < metal in order to compensate for differences in tape characteristics. Further, since normal tape has a large loss in the high frequency region, the gain is particularly high in the high frequency region. The gain of the recording equalizer section in the circuit shown in Figure 3 is determined by the impedance connected between the - side input terminal and the output terminal/the impedance grounded from the - side input terminal. Since the gain increases if the grounded impedance is reduced, the gain correction due to the difference in tape type described above is performed by using the transistor 22 when using chrome tape.
is turned on and one end of the capacitor 48 and resistor 49 are grounded, or in the case of a metal tape, the transistor 16 is turned on and one end of the capacitor 50 and resistor 51 is grounded. Further, the correction of the high frequency part of the normal tape is realized by lowering the resonance frequency in series resonance between the coil 47 and the capacitor 46 by adding the capacitor 45 when the transistor 28 is turned on. In this way, the recording equalizer amplifier is switched depending on the type of tape. The recording bias current is switched by controlling the voltage supplied to the bias current generating section 58 using the transistor 55.
That is, the voltage supplied to the bias current generator is determined by the base voltage of the transistor 55,
This is because the voltage of the second power supply 56 is approximately determined by the voltage division ratio between the resistor 57 and the resistor grounded from the base of the transistor 55. Therefore, by turning on the transistors 18, 24, and 30 according to the type of tape, that is, by connecting the resistors 52, 53, and 54 from the base of the transistor 55 to ground, the optimum bias current can be set to the recording head 4.
1 can be supplied. However, in this conventional configuration, the output is created by logically processing the signal corresponding to each tape from the detection signal of the detection hole by the switch, so a combination of logic circuits is always required, resulting in a complicated configuration and an expensive It was a detection switching device. OBJECTS OF THE INVENTION The present invention solves the above-mentioned drawbacks, and an object of the present invention is to provide a detection switching device with a simple configuration that does not use a combination of complicated logic circuits. Structure of the Invention The present invention provides a diode and tape type display device.
By effectively utilizing the switching operation of the LED itself, the detection switching device is realized without using a complicated logic circuit. DESCRIPTION OF THE EMBODIMENTS FIG. 4 is a circuit diagram of essential parts showing an embodiment of the detection switching device of the present invention. 61 is a leaf switch for detecting chrome tape, 62 is a leaf switch for detecting metal tape, and one end b of each is +
It is connected to a power source 63. Reference numeral 64 is an LED for normal tape display, and its anode is connected to the + power supply 63, and its cathode side is grounded via a resistor 65 and connected to the cathode side of a diode 66. 67 is for chrome tape display
It is an LED, and its anode side is connected to the other end a of the leaf switch 61 and the anode side of the diode 66, and its cathode side is connected to the anode side of the diode 68. Reference numeral 69 denotes an LED for metal tape display; its anode side is connected to the other end a of the leaf switch 62, and its cathode side is grounded via the cathode side of a diode 68 and a resistor 70. The above configuration is the part indicated by a broken line 71 in the figure. Next, the configuration of the peripheral circuit related to the broken line section 11 will be explained. 72 is a bias current generating section 7
This is a transistor for controlling the voltage supplied to the transistor 3, and its collector is connected to the + power supply 63, and its emitter is connected to the bias current generating section 73. The base is connected to the + power supply 63 via a resistor 74 and to the anode side of a diode 75. The cathode side of the diode 75 is connected to a -power supply 77 via a resistor 76, to the cathode side of a diode 79 via a resistor 78, and to the cathode side of a diode 81 via a resistor 80. The anode side of the diode 79 is connected to the a terminal of the leaf switch 62, and the anode side of the diode 81 is connected to the a terminal of the leaf switch 61. Reference numeral 82 is a transistor for switching when a metal tape is used in the recording equalizer, and its emitter is grounded and its base is connected to the a terminal of the leaf switch 62 via a resistor 83. 84 is a transistor for switching the chrome tape of the recording equalizer, the emitter is grounded and the base is connected to the leaf switch 6 via the resistor 85.
It is connected to the a end of 1. 86 is a P-type field effect transistor (hereinafter abbreviated as FET) for switching the recording equalizer during normal tape mode, and its source is grounded and its gate is connected to one end of a resistor 87. The other end of the resistor 87 is connected to the a end of the leaf switch 61 via a resistor 88 and a resistor 89.
- connected to the power supply 67 via. Reference numeral 90 denotes an N-type FET for switching a reproduction equalizer, whose source is grounded and whose gate is connected to one end of a resistor 91. The other end of the resistor 91 is connected to the a terminal of the leaf switch 61 via a resistor 92 and to the negative power source 77 via a resistor 93. The operation of this embodiment configured as above will be described below. During normal tape, both the leaf switch 61 and the leaf switch 62 are off, so the LED 69 does not light up, and since the diode 66 is in the opposite direction, no current flows and the LED 67 does not light up. Therefore, the LED 4 for normal tape display
only lights up. Also, when using chrome tape, leaf switch 61
is on and leaf switch 62 is off.
The LED 69 does not light up, but the LED 67 for displaying the chrome tape has + power supply 63 → leaf switch 61 → LED 67 → diode 68 → resistor 70 →
Since current flows through the path called ground, the LED 67 for displaying the chrome tape lights up. At the same time, the leaf switch 61 is on, so the diode 6
6 are connected in parallel to the LED 64 in the same direction, and the LED 64 for normal tape display is turned off. because
The ON voltage of an LED is generally about 2V, and the forward ON voltage of a diode is 0.7V, so the voltage across the LED 64 becomes the ON voltage of the diode 66, which is about 0.7V, and the LED 64 has a current of 0.7V. This is because the light does not flow and the light goes out. On the other hand, when using metal tape, leaf switch 61,
62 are both turned on, and the metal tape display
LED69 lights up. For normal tape display
The LED 64 is turned off for the same reason as in the case of the chrome tape, that is, due to the parallel connection of the diode 66 when the leaf switch 61 is turned on. Regarding LED67 for displaying chrome tape, please refer to the LED
It will not light up unless about 2.7V, which is the sum of about 2V of on voltage of LED 67 and about 0.7V of on voltage of diode 68, is applied between the anode side of LED 67 and the cathode side of diode 68, but in this case, LED 69 is connected in parallel here. Since it is connected to , the voltage will be approximately 2V, and the LED 67 for displaying the chrome tape will turn off. In this way, for displaying tape type according to each tape type.
The LED lights up. Other reproduction equalizers, recording equalizers, and recording bias currents are switched by the voltages at the a end of the leaf switch 61 and the a end of the leaf switch 62. The bias current is switched by the voltage supplied to the bias current generating section 73, and the bias current changes approximately in proportion to the supplied voltage.
The supply voltage is controlled by the transistor 72 and is almost equal to its base voltage, so the resistance from the power supply 63 to the base is set to 74 when using a normal tape.
In addition, the bias current is switched by using parallel resistances such as a resistor 74 and a resistor 80 when using a chrome tape, and using parallel resistances including a resistor 74, a resistor 80, and a resistor 78 when using a metal tape. Generally, the optimum bias current for each tape is in the order of metal > chrome > normal, so it can be achieved by switching the resistance value as described above. Recording equalizer switching is FET in normal mode
86, transistor 84 when using chrome tape
When a metal tape is used, switching is performed using transistors 82 and 84. The reproduction equalizer is switched using FET90. As described above, according to this embodiment, LED64, LED67, LED
By utilizing the difference between the on-voltage of 69 and the on-voltages of diode 66 and diode 68,
without using a combination of special logic circuits,
Automatic detection and switching of tape types can be achieved with a simple configuration. Effects of the Invention As described above, the present invention can realize a detection switching device with a simple configuration and at low cost by switching the LED on and off based on the difference in the on-voltage of the LED and the diode. It's large.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the detection hole for detecting the tape type in the cassette half, Fig. 2 is a side view of the configuration for detecting the detection hole, Fig. 3 is a circuit diagram showing a conventional detection switching device, and Fig. 4 1 is a main circuit diagram showing an embodiment of a detection switching device of the present invention. FIG. 61, 62... Leaf switch, 63... + power supply, 64, 67, 69... Light emitting diode, 6
6, 68...Diode, 65, 70...Resistor,
72...Transistor, 73...Bias current generating section, 74, 78, 80...Resistor, 75, 79,
81...Diode.

Claims (1)

[Claims] 1 A chrome tape detection hole detection switch and a metal tape detection hole detection switch are respectively provided corresponding to the chrome tape detection hole and metal tape detection hole provided in the cassette half, and one end of the two detection switches is connected in common. and connect it to the power supply.
The other terminal of the chrome tape detection hole detection switch has an anode of a first diode, a first output end, and a second diode arranged in series in the forward direction. Connect the second output end to the other terminal of the metal tape detection hole detection switch and the anode of the metal tape display light emitting diode, and connect the cathode side of the metal tape display light emitting diode to the other terminal of the metal tape detection hole detection switch. It is connected to the cathode of a second diode arranged in series with the display light emitting diode, and this connection point is grounded via a first resistor, and the anode side of the first diode is connected to a power source. Connect the cathode side of the normal tape display light emitting diode connected to the normal tape display and one end of the second resistor, and ground the other end of the second resistor, and when only the chrome tape detection hole detection switch is conductive, the chrome tape display will be displayed. When both the chrome tape detection hole detection switch and the metal tape detection hole detection switch are conductive, only the metal tape display light emitting diode is lit, and both of the detection switches are nonconductive. The recording bias current, the recording equalizer characteristic, and the playback equalizer characteristic are configured to be configured so that only the light emitting diode for displaying the normal tape is turned on at some time, and the recording bias current, the recording equalizer characteristic, and the playback equalizer characteristic are switched using the voltage change at the first and second output terminals. A detection switching device characterized by: