JPS642246Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching circuit for a tape recorder incorporating two tape recorders.

Recently, tape recorders having two built-in tape recorders have become popular, and the playback signals of such tape recorders are emitted by using a single speaker. In a tape recorder configured in this way, it is necessary to switch the signal input to the main amplifier circuit to which the speaker is connected as a load, and such switching is performed by multiple mechanical switches. The problem was that it became complicated.

The present invention has been developed in view of these points, and will be described in detail below with reference to the illustrated embodiments. In the figure, 1 is a magnetic head for a first tape recorder, and 2 is a first preamplifier circuit to which a signal reproduced by the first magnetic head 1 for a tape recorder is input and which amplifies the reproduced signal. , transistors 3, 4, and 5, etc. 6 is a magnetic head for the second tape recorder; 7 is a magnetic head 6 for the second tape recorder;
This is a second preamplifier circuit to which a signal reproduced by the amplifier is input and which amplifies the reproduced signal, and is composed of transistors 8, 9, 10, etc. 11 is a variable resistor to which the output signals of the first preamplifier circuit 2 and the second preamplifier circuit 7 are applied and adjusts the signal level; 12 is a variable resistor whose level is adjusted by the variable resistor 11; This is a main amplification circuit into which a signal is input and amplifies the signal, and a speaker 13 is connected as a load. 14 is a first switch that is closed during playback operation of the first tape recorder; 15 is the first switch 1;
When 4 is closed, the first electric motor is supplied with power and rotates, and has the function of driving the magnetic tape of the first tape recorder to run. 1
6 is a second switch that is closed when the second tape recorder is operated; 17 is a second electric motor that is supplied with power and rotates when the second switch 16 is closed; It has the function of driving the magnetic tape to run. 18 is a control transistor whose emitter is connected to a power supply and whose base is connected to the power supply terminal side of the first switch 14 via a resistor 19; its collector is connected to a resistor 20 and a diode 2;
1 to the base of a transistor 4 constituting the first preamplifier circuit 2. Further, the power supply terminal of the first switch 14 is connected to a resistor 2.
a capacitor 2 connected between the anodes of the diodes 21 and 23 and ground, the capacitor 2 being connected to the base of the transistor 9 constituting the second preamplifier circuit 7 via the anode 2 and the diode 23;
4 and 25 serve to absorb sudden voltage fluctuations that occur when power is supplied or cut off, and to prevent the occurrence of shock noise.

In addition to the above, the switching circuit of the present invention is constructed, and the operation of the circuit will be explained next. When the first tape recorder is operated for reproduction, the first switch 14 is closed and the drive mechanism of the first tape recorder is put into the reproduction operation state, and the magnetic tape is driven at a constant speed by the rotation of the first electric motor 15. In such a state, the control transistor 18
is reverse biased and in a non-conducting state, so no high voltage is applied to the base of the transistor 4 constituting the first preamplifier circuit 2 via the diode 21, and the first preamplifier circuit 2 In working condition. In addition, in such a state, the first switch 14,
Since a high voltage is applied to the base of the transistor 9 constituting the second preamplifier circuit 7 via the resistor 22 and the diode 23, the transistor 9 is reverse biased and is in a non-conducting state, and the second preamplifier circuit 7 is in a non-conducting state. Circuit 7 is inactive. When the first tape recorder is operated for reproduction, it enters the operating state described above, and the signals recorded on the magnetic tape are reproduced by the magnetic head 1 for the first tape recorder. The reproduced signal reproduced by the first tape recorder magnetic head 1 is input to the first preamplifier circuit 3, amplified, and then applied to the variable resistor 11. The reproduced signal applied to the variable resistor 11 is level-adjusted and then input to the main amplifier circuit 12 where it is amplified and emitted by the speaker 13.
The reproduction operation of the first tape recorder is performed in this manner, and next, the reproduction operation of the second tape recorder will be explained. When the second tape recorder is operated for reproduction, the second switch 16 is closed and the drive mechanism of the second tape recorder is put into the reproduction operation state, and the second electric motor 17 rotates to drive the magnetic tape at a constant speed. In such a state,
Since the control transistor 18 is forward biased and conductive, a high voltage is applied to the base of the transistor 4 constituting the first preamplifier circuit 2 via the emitter-collector path of the control transistor 18, the resistor 20 and the diode 21. applied. As a result, the transistor 4 is reverse biased and becomes non-conductive, so the first preamplifier circuit 2 becomes inoperative. On the other hand, since no high voltage is applied to the base of the transistor 9 constituting the second preamplifier circuit 7 via the diode 23, the second preamplifier circuit 7 is in an operating state. When the second tape recorder is played back, it enters the operating state described above, and the signals recorded on the magnetic tape are transferred to the second tape recorder.
After being reproduced by the tape recorder magnetic head 6, the signal is input to the second preamplifier circuit 7 which is in operation. The reproduced signal input to the second preamplifier circuit 7 is amplified and then applied to a variable resistor 11 to adjust its level. The reproduced signal whose level has been adjusted by the variable resistor 11 is sent to the main amplifier circuit 12.
After being amplified, the signal is applied to the speaker 13 and emitted.

As described above, the first tape recorder and the second tape recorder
The operation when playing back one tape recorder alone will be performed, the next operation will be when playing back two tape recorders individually, but the next time the playback operation on two tape recorders will be performed simultaneously. The operation when this is done will be explained.
If playback operations are performed on the first tape recorder and the second tape recorder at the same time, the first switch 14
Then, the second switch 16 is closed, and the drive mechanism of each tape recorder is put into the playback state, so that the respective magnetic tapes are driven to run at a constant speed. In such a state, a reverse bias voltage is applied to the base of the control transistor 18 through the first switch 14, so that the control transistor 18 is in a non-conducting state and the first preamplifier circuit 2 is in an operating state. On the other hand, the second preamplifier circuit 7 is in an inoperative state because a high voltage is applied to the base of the transistor 9 via the first switch 14, the resistor 22, and the diode 23. Therefore, in such a state, the reproduced signal reproduced by the second tape recorder magnetic head 6 is not outputted from the second preamplifier circuit 7, and is not outputted by the first tape recorder magnetic head 1. Only the reproduced signal is transmitted to the first preamplifier circuit 2.
The signal is amplified by and applied to the variable resistor 11.
Therefore, the signal reproduced by the first tape recorder magnetic head 1 is applied to the speaker 13 and the sound is emitted. In this state, when the playback mode of the first tape recorder is released, the first switch 14 is opened, so that the control transistor 18, which was in a non-conducting state, is reversed to a conducting state. As a result, the first preamplifier circuit 2 becomes inactive and the second preamplifier circuit 7 becomes active, so that the second tape recorder magnetic head 6
The reproduced signal is applied to the speaker 13 through the second preamplifier circuit 7, the variable resistor 11, and the main amplifier circuit 12, and is emitted as sound.

In this embodiment, power is supplied to the first electric motor 15 and the second electric motor 17 through the first switch 14 and the second switch 16, but it can also be configured to be supplied through a drive transistor or the like. Also, a PNP type transistor was used as the control transistor 18, but
Not only can an NPN type transistor be used, but also multiple transistors can be used. Further, in this embodiment, the amplification operation is controlled by making the transistors constituting the first preamplifier circuit 2 and the second preamplifier circuit 7 non-conducting. You can also force it. Further, capacitors 24 and 25 connected between the anodes of diodes 21 and 23 and the ground have a filter function for removing ripple components generated from the motor in addition to the above-mentioned noise prevention function.

As explained above, the switching circuit of the present invention performs the signal switching operation using the minimum number of mechanical switches, so the configuration is extremely simple.
This is very effective when applied to a tape recorder with two built-in tape recorders.

[Brief explanation of the drawing]

The illustrated circuit is one embodiment of the switching circuit of the present invention. Explanation of main figure numbers, 1... First magnetic head for tape recorder, 2... First preamplifier circuit, 6...
Magnetic head for second tape recorder, 7...Second
Preamplifier circuit, 12... Main amplifier circuit, 14... First switch, 15... First electric motor, 16... Second
Switch, 17...second electric motor, 18...control transistor.

Claims (1)

[Scope of utility model registration request] In a tape recorder incorporating first and second tape recorders, a first preamplifier circuit amplifies the signal reproduced by the first tape recorder magnetic head, and a first preamplifier circuit amplifies the signal reproduced by the second tape recorder magnetic head. a second preamplifier circuit for amplifying a signal; a main amplifier circuit to which the output signals of the first preamplifier circuit and the second preamplifier circuit are input, and to which a speaker is connected as a load;
A first switch that is closed when the tape recorder is in playback operation, a second switch that is closed when the second tape recorder is in playback operation, and when the first switch is closed, driving current is supplied and the first tape is The first part that drives the recorder's magnetic tape.
A second electric motor, to which driving current is supplied when the second switch is closed and drives the magnetic tape of the second tape recorder, is in a conductive state when the first switch is in an open state and is in a conductive state. a control transistor which is inverted to a non-conducting state when the first switch is closed; a direct current voltage applied to a bias circuit of a transistor constituting an amplifier circuit to disable the second preamplifier circuit, and obtained through the control transistor which is in a conductive state when the second tape recorder is in a playback operation state; A switching circuit for a tape recorder, characterized in that the first preamplifier circuit is rendered inoperable by being applied to a bias circuit of a transistor constituting the first preamplifier circuit.