JPS624Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a tape recorder recording and playback system that does not generate noise or oscillate even when switching from the recording state to the playback state while voltage is applied to the amplifier circuit. Regarding switching circuits.

In a tape recorder for language practice or for taking notes, if you press the rewind button from the recording state in order to quickly play back the recorded content, the record button returns and the review state is set at the same time, and when the rewind button is released, the rewind button is pressed. It is configured to immediately enter the playback state.

In this case, since the recording/playback selector switch is switched while voltage is applied to the amplifier circuit, transient noise occurs, and there is also a time delay between each switch element of the recording/playback selector switch, so in the worst case, the input side and output It is also conceivable that the two sides may be coupled and oscillate.

The present invention relates to a recording/playback switching circuit for a tape recorder that is free from such concerns, and will be described below with reference to the drawings.

1 is a magnetic head for both recording and playback, 2 is an erasing head, 3 is a microphone, 4 is a preamplifier circuit, 5 is a main amplifier circuit, 6 is a speaker, 7 is a bias oscillation circuit, 8 to 11 are recording base selection switches. It is. 1
2 is a first switch which is turned off first when changing the recording/playback switch 8 to 11 from the recording state to the playback state.
The switch 13 is a second switch for power supply, and 14 is a first transistor, which is turned on and off by the first switch 12 and the recording/playback changeover switch 9. 1
5 is a time constant circuit consisting of resistors 16, 17 and a capacitor 18, and 19 is a second transistor, which is connected to ground the output side of the preamplifier circuit 4. 20 is a motor.

Next, the operation of the present invention will be explained. The illustrated recording/reproduction changeover switches 8 to 11 indicate the recording state, and a bias voltage is applied to the base of the first transistor 14, so that the first transistor 14 is turned on. Therefore, the capacitor 18 of the time constant circuit 15 is not charged. Now, when recording is finished and the rewind button is pressed, the second switch 13 remains on, but the first switch 12 is turned off, causing the bias oscillation circuit 7 to operate downward, and at the same time turning off the first transistor 14. . Then, a charging current flows into the capacitor 18 via the resistor 16, turning on the second transistor 19. When the rewind button is pressed, the record button returns to its original position, so each of the recording and playback switches 8 to 11 is also switched with respect to the first switch 12, and at this time there is a possibility that switching noise may be generated. Even if the signal is generated, the output of the preamplifier circuit 4 is grounded by the second transistor 19, so it will not be transmitted to the main amplifier circuit 5 at the subsequent stage. When the capacitor 18 of the time constant circuit 15 is fully charged, the second transistor 19 is turned off because no bias voltage is applied to it, and after that, the output of the first transistor 4 is directly transmitted to the main amplifier circuit 5. Ru. While the rewind button is being pressed, rewinding is performed during that time, and when the pressing force on the rewind button is released, the playback mode immediately returns to that state.

As described above, in the recording/playback switching circuit of the tape recorder of the present invention, when switching the recording/playback switch from the recording state to the playback state, a switch connected outside the signal circuit in addition to the recording/playback switch is operated first, and then the switch is connected to the outside of the signal circuit. The first transistor is controlled and the second transistor is turned on or off via a time constant circuit to temporarily put the amplifier circuit in a non-operating state, so the circuit can be switched from the recording state to the playback state while the amplifier circuit is operating. No noise is generated either.

[Brief explanation of the drawing]

The figure is a recording/playback switching circuit diagram of the tape recorder of the present invention. 4... Preamplifier circuit, 5... Main amplifier circuit, 8~
11...Record/playback selector switch, 12...First switch, 13...Second switch, 14...First transistor, 15...Time constant circuit, 19...Second switch
transistor.

Claims (1)

[Scope of utility model registration request] A magnetic head for both recording and playback purposes and an amplification circuit for both recording and playback purposes are put into the recording or playback state using multiple sets of recording and playback selector switches while the power switch is on, and the amplification circuit is connected to a separate circuit from the signal path. An open/close switch that is operated before a recording/playback switch when switching a circuit from a recording state to a playback state, a first transistor that is turned on and off by the open/close switch, and a time constant circuit that is charged and discharged by the first transistor. and a second transistor for disabling the amplifier circuit for a predetermined period of time limited by the time constant circuit.