JPH0425661Y2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field The present invention relates to a voltage check circuit for checking the power supply voltage of a tape recorder that uses a battery as a power source.

(B) Background Art A tape recorder that uses a battery as a power source is equipped with a voltage check circuit because it is necessary to check the power supply voltage, but the check level is set by taking into account the characteristics of the amplifier circuit and electric motor. . Also, recently, most of the preamplifier circuits and main amplification circuits that make up tape recorders are integrated circuits (ICs).
has been made into Among such tape recorders, those equipped with a noise reduction circuit that reduces tape hiss noise are becoming popular, and most of these noise reduction circuits are also integrated circuits. The minimum operating voltage required for the above-mentioned preamplifier circuit and main amplifier circuit to operate normally is generally lower than the minimum operating voltage of the noise reduction circuit, and the operation or non-operation of the noise reduction circuit is determined by a selection switch. The switch is controlled by the switch. In a tape recorder with such a built-in noise reduction circuit, when the check level of the voltage check circuit is adjusted to the minimum operating voltage of the preamplifier circuit and main amplifier circuit, the power supply voltage drops to a voltage at which the noise reduction circuit cannot operate normally. Despite this, the voltage check circuit will display that the voltage is normal. On the other hand, if the check level of the voltage check circuit is set to the minimum operating voltage of the noise reduction circuit, the voltage check circuit will indicate that the power supply voltage has dropped to an unusable voltage even though the noise reduction circuit is not used. Become.

(c) Purpose of the invention The purpose of the invention is to provide a circuit for a tape recorder equipped with a noise reduction circuit, which switches the check level of the voltage check circuit depending on whether the noise reduction circuit is used or not. It is something.

(d) Embodiment of the invention The illustrated circuit is an embodiment of the voltage check circuit of the invention. In the figure, 1 is a magnetic head that reproduces the signal recorded on the magnetic tape, 2 is a preamplifier circuit that amplifies the signal reproduced by the magnetic head 1 and is implemented as an IC, and 3 is an IC-based preamplifier circuit. an input terminal 4 and an output terminal 5 to which the output signal of the preamplifier circuit 2 is applied.
It is equipped with Reference numerals 6 and 7 indicate selection switches which are switched in conjunction and select operation or non-operation of the noise reduction circuit 3; one selection switch 6
is inserted into the power supply line to the noise reduction circuit 3, and the other selection switch 7 is connected to bypass the noise reduction circuit 3. 8 is a variable resistor to which the signal passed through the noise reduction circuit 3 or the selection switch 7 is applied and whose level is adjusted; 9 is a variable resistor which amplifies the signal whose level has been adjusted by the variable resistor 8; and IC
10 is a speaker connected as a load of the main amplification circuit 9, and 11 is a battery that supplies power to the preamplification circuit 2, the noise reduction circuit 3, the main amplification circuit 9, etc. . 12 and 13
is the first line connected in series between the power supply line 14 and ground.
and a second voltage dividing resistor, 15 is an interlocking switch 1 which is switched in conjunction with the selection switches 6 and 7.
6 has an emitter grounded and a collector connected to the first voltage dividing resistor 12 via the third voltage dividing resistor 17.
and a switching transistor connected to the voltage dividing point A by the second voltage dividing resistor 13, and its base is connected to the power supply line 14 via the resistor 18 and the interlocking switch 15. Reference numeral 19 denotes a voltage check circuit, which is configured to display the state of the power supply voltage using a light emitting diode or the like. 2
Reference numeral 0 designates a check switch that is closed when checking the power supply voltage, and is connected so as to lead the voltage at the voltage dividing point A of the first voltage dividing resistor 12 and the second voltage dividing resistor 13 to the voltage checking circuit 19. has been done. In such a circuit, the minimum working voltage of the preamplifier circuit 2 and the main amplifier circuit 9 is V ₁ , and the noise reduction circuit 3 is
Letting the minimum working voltage of V2 be _V2 , there is a relationship of _V1 < _V2 . Further, the resistance values of the first voltage dividing resistor 12, the second voltage dividing resistor 13, and the third voltage dividing resistor 17 are the same as those of the noise reduction circuit 3.
Voltage check _{circuit 19}
The display state of the display elements constituting the screen is set to change.

The present invention is constructed as described above, and its operation will be explained next. In the illustrated state, the noise reduction circuit 3 is not in use, and the interlocking switch 15 is open, so that the switching transistor 1 is not in use.
6 is in a non-conducting state. In this state, the signal reproduced by the magnetic head 1 is amplified by the preamplifier circuit 2 and then applied to the variable resistor 8 through the selection switch 7 which is in the closed state. The reproduced signal applied to the variable resistor 8 is amplified by the main amplifier circuit 9 and then applied to the speaker 10 to emit sound. When a voltage check operation is performed in such a state, the voltage at the voltage division point A is applied to the voltage check circuit 19 by closing the check switch 20. When the voltage of the power supply line 14 is higher than the minimum working voltage _V1 of the preamplifier circuit 2 and main amplifier circuit 9, the voltage check circuit 19 indicates that normal operation can be performed. When the battery 11 is exhausted and the voltage of the power supply line 14 becomes lower than _V1 , the display state of the voltage check circuit 19 changes to indicate that normal operation cannot be performed.

As described above, the operation is performed when the noise reduction circuit 3 is not used. Next, the operation when the noise reduction circuit 3 is used will be explained. Selection switch 6
and 7, power is supplied to the noise reduction circuit 3 and the noise reduction circuit 3 is put into operation, and when the interlocking switch 15 is closed, a bias current is supplied to the switching transistor 16, so that the switching transistor 16 becomes conductive. Therefore, in such a state, the third voltage dividing resistor 17 is connected in parallel to the second voltage dividing resistor 13. The signal reproduced by the magnetic head 1 is amplified by a preamplifier circuit 2 and then applied to an input terminal 4 of a noise reduction circuit 3. The reproduced signal input to the noise reduction circuit 3 is outputted to the output terminal 5 after being subjected to noise reduction processing. The signal output to the output terminal 5 is level-adjusted by a variable resistor 8 and then input to the main amplifier circuit 9.
The reproduced signal input to the main amplification circuit 9 is amplified and then applied to the speaker 10 to emit sound. In such a state, when a voltage check operation is performed, the voltage at the voltage dividing point A is applied to the voltage check circuit 19 by closing the check switch 20. In such a state, since the third voltage dividing resistor 17 is connected in parallel to the second voltage dividing resistor 13, the voltage of the power supply line 14 is divided to a lower level than when the noise reduction circuit 3 is not used. It is in a state where it is input to the voltage check circuit 19. When the voltage of the power supply line 14 is higher than the minimum working voltage _V2 of the noise reduction circuit 3, the voltage check circuit 19 indicates that normal operation can be performed. When the battery 11 is exhausted and the voltage of the power supply line 14 becomes lower than _V2 , the display state of the voltage check circuit 19 changes to indicate that normal operation cannot be performed.

If the voltage of the power supply line 14 is higher than _V2 , the tape recorder operates normally regardless of whether the noise reduction circuit 3 is used, and if it is lower than _V1 , the noise reduction circuit 3 is not used. The tape recorder does not function normally regardless of use. Next, the voltage of the power supply line 14 is higher than V ₁ and V ₂
The case where it is lower will be explained. In such a state, the preamplifier circuit 2 and the main amplifier circuit 9 can operate normally, but the noise reduction circuit 3 cannot operate normally. The user uses the noise reduction circuit 3
When a voltage check operation is performed after operating the selection switches 6 and 7 to operate the voltage check circuit 19, it is displayed that the voltage check circuit 19 is in a state in which normal operation cannot be performed as described above. After recognizing from this display that the power supply voltage has dropped, the user switches the selection switches 6 and 7 to disable the noise reduction circuit 3. When such a switching operation is performed, the voltage check circuit 19 indicates that normal operation can be performed as described above. Therefore, if the user performs a reproduction operation, the reproduced signal can be heard even though the noise reduction circuit 3 does not operate.

(E) Example of application of the invention In the embodiment, the selection switch 6 controls the power supply to the noise reduction circuit 3, and the selection switch 7 bypasses the signal. may be provided to control the inoperability of the circuit and a bypass signal path may also be incorporated. Furthermore, although the voltage input to the voltage check circuit 19 is switched by turning the switching transistor 16 on and off, the sensitivity of the voltage check circuit 19 can also be switched.

(F) Effect The present invention is designed to switch the check level of the voltage check circuit depending on whether the noise reduction circuit is activated or not in a tape recorder incorporating a noise reduction circuit whose minimum working voltage is higher than the minimum working voltage of the amplifier circuit. Therefore, it is possible to recognize whether or not the noise reduction circuit operates normally in each state of use and non-use.

[Brief explanation of drawings]

The illustrated circuit is one embodiment of the voltage check circuit of the present invention. Explanation of main drawing numbers, 2... Preamplifier circuit, 3...
Noise reduction circuit, 6, 7...Selection switch, 9...
Main amplifier circuit, 12... First voltage dividing resistor, 13... Second voltage dividing resistor, 15... Interlocking switch, 17... Third voltage dividing resistor, 19... Voltage check circuit, 20...
...Check switch.

Claims (1)

[Scope of utility model registration request] In a tape recorder that uses a battery as a power source and is equipped with a voltage check circuit that checks the power supply voltage, a preamplifier circuit that amplifies a signal reproduced by a magnetic head and is implemented as an IC,
A main amplification circuit which further amplifies the signal amplified by the preamplifier circuit and is integrated circuit; It consists of a high noise reduction circuit, a selection switch that selects whether to operate or disable the noise reduction circuit, and an interlocking switch that is switched in conjunction with the switching of the selection switch and also switches the check level of the voltage check circuit. A voltage check circuit for a tape recorder, characterized in that the check level of the voltage check circuit when the reduction circuit is in an operating state is higher than the check level when the reduction circuit is in an inactive state.