JPS6336506Y2 - - Google Patents

Description

[Detailed description of the invention] This invention keeps the playback operation button and the fast forward (rewind) operation button in the operating state, runs the magnetic tape at high speed, and automatically selects a song, and the no-signal detection circuit operates. Therefore, the present invention relates to an improvement of an automatic music selection tape recorder which, after detecting a no-signal portion between songs on a tape, drives an electromagnetic plunger to release a fast forward (rewind) operation button and switch to a playback state. In such an automatic music selection tape recorder, a large current flows through the electromagnetic plunger to drive the electromagnetic plunger when a no-signal portion between songs is detected. Also, at this time, a mechanical operation is performed to unlock the fast forward (rewind) operation button, so when the plunger is driven, mechanical noise and electrical noise are mixed into the audio amplification circuit and generated from the speaker. Easy,
It may cause discomfort to the user. Conventional automatic music selection tape recorders are often equipped with a muting circuit to attenuate the chirping and chirping sounds that occur in the automatic music selection state. The operation of the circuit had already ended, and no consideration had been taken to prevent the generation of mechanical and electrical noise when the plunger was driven. The present invention provides an automatic music selection tape recorder designed to easily prevent noise generation during plunger drive.The circuit configuration of the present invention shown in the drawings will be explained below. Reference numeral 1 designates a playback head that comes into contact with a magnetic tape 2 running at high speed when both a playback operation button and a fast forward (rewind) operation button are held in the operating state, and 3 an amplifier that amplifies the output of the playback head. 4 is a Schmitt circuit 9 consisting of a level determination transistor 5, a first time constant circuit 6, inverters 7 and 8;
This is a no-signal detection circuit composed of a time constant circuit 10 and a 3-input NAND gate 11. 12 is a switching transistor whose base is connected to the output of the three-input NAND gate 11; 13 is connected between the collector/emitter of the switching transistor 12, the series circuit of the electromagnetic plunger 14, and the power supply +B; a first switch 15 that is closed when the regeneration operation button is operated; 15 is a second switch whose one end is connected to the connection point between the series circuit and the first switch 13; and a second switch 15 that is closed when the regeneration operation button is operated; Reference numeral 16 denotes a Schmitt circuit consisting of inverters 17 and 18, whose input terminal is connected to the other terminal of the second switch 15, a diode 19, and a resistor 20.
The output terminal of the Schmitt circuit 16 is connected via an inverter 21 to the first input terminal a of the three-input NAND gate 11 in the no-signal detection circuit 4. 22 is a capacitor connected between the connection point of the diode 19 and resistor 20 and the power supply +B; 23 is the Schmitt circuit 16;
A muting transistor whose base is connected to the output terminal of the mutating transistor 2.
3 is connected to the audio amplification circuit 24 as is well known. The tape recorder of the present invention is constructed as described above, and its operation will be explained below. When the playback operation button and the fast forward (or rewind) operation button are held in the operating state for automatic music selection operation, the first switch 13 and the second switch 15 are closed. Therefore, the power supply +B is connected to one end of the electromagnetic plunger 14 through the first switch 13, and the first
A high level is supplied to the input terminal of the Schmitt circuit 16 through the second switches 13 and 15, the diode 19, and the resistor 20. Since the output terminal of the Schmitt circuit 16 outputs a high level, the muting transistor 23 is activated, and the first input terminal a of the 3-input NAND gate 11 is set to a low level via the inverter 21. , the no-signal detection circuit 4 is placed in an operation standby state for automatic music selection. At this time, when a signal on the magnetic tape 2 is being reproduced by the reproducing head 1, the level determining transistor 5 is conductive and the second input terminal b of the three-input NAND gate 11 is set to high level through the Schmitt circuit 9. 3 input terminal c is set to low level. On the other hand, if the no-signal part between tracks of the magnetic tape 2 faces the playback head 1 and the signal from the playback head 1 disappears, the level judgment transistor 5 becomes non-conductive, so that the first time constant circuit 6 According to the attenuation characteristic determined by a constant, the input terminal of the Schmitt circuit 9 becomes a low level, the second input terminal b of the 3-input NAND gate 11 becomes a low level, and the third input terminal c becomes the time constant of the second time constant circuit 10. The 3-input NAND gate 11 is at low level for the time determined by
The output is at high level for a certain period of time. Therefore, the switching transistor 12 is activated by the high level output of the three-input NAND gate 11.
conducts, the electromagnetic plunger 14 is driven, and the operation of the electromagnetic plunger 14 releases the fast-forward (or rewind) operation button and switches the first switch 1
3 is released, the song selection state ends, and the playback state begins. According to the tape recorder of the present invention, at this time, the capacitor 22, which had been short-circuited by the first and second switches 13, 15 and the diode 19, now
Since the short circuit is removed by opening the first switch 13, a charging current i flows through the capacitor 22, and the output terminal of the Schmitt circuit 16 is held at a high level for a period of time until the charging is completed. The muting transistor 23 is maintained in its operating state. And such a capacitor 22
The charging current is prevented from flowing into the electromagnetic plunger 14 by the diode 19. Note that when the power is turned on by a power switch (not shown), the capacitor 22 is charged, but in the automatic music selection state where the first switch 13 and the second switch 15 are closed, the capacitor 22 is charged. 2
The charged charges No. 2 are discharged, and the no-signal detection circuit 4 enters the operation standby state as described above. As mentioned above, in the automatic music selection tape recorder of the present invention, after the no-signal detection circuit detects the no-signal portion between songs, the electromagnetic plunger is driven to release the fast-forward (rewind) operation button, and then the capacitor is charged. Since the structure is configured such that the muting transistor of the audio amplification circuit can be kept in the operating state for a certain period of time, mechanical noise and electrical noise generated through the audio amplification circuit when changing from the song selection state to the playback state can be prevented. This can be easily prevented and is useful in practice.

[Brief explanation of the drawing]

The figure is a circuit diagram of the automatic music selection tape recorder of the present invention. 4 ... No signal detection circuit, 12... Switching transistor, 13... First switch, 14...
Electromagnetic plunger, 15...Second switch, 16...
...Schmitt circuit, 19...diode, 22...
...capacitor, 23...mutating transistor.

Claims (1)

[Scope of utility model registration request] The playback operation button and the fast forward (rewind) operation button are held in the operating state, the magnetic tape is run at high speed, and the automatic song selection state is established, and the no-signal detection circuit detects the no-signal portion between songs on the tape. In an automatic music selection tape recorder which, after detection, drives an electromagnetic plunger to release a fast forward (rewind) operation button and enter a playback state, a switching transistor controlled by the no-signal detection circuit; a first switch that is connected between the collector/emitter of the switching transistor, the series circuit of the electromagnetic plunger, and the power supply and is closed when the fast forward (rewind) operation button is operated; and a connection point between the series circuit and the first switch. a second switch having one end connected to the regeneration operation button and closed when the playback operation button is operated; a Schmidt circuit connected via a diode between the other end of the second switch and the no-signal detection circuit; a capacitor connected between a connection point between a diode and a Schmitt circuit and a power supply; and a muting transistor of an audio amplification circuit connected to an output terminal of the Schmitt circuit;
When the switches are both closed, the no-signal detection circuit is set to an operation standby state through the Schmitt circuit, and at the same time the muting transistor is activated, and the no-signal detection circuit is activated and fast-forwards (rewinds) by the electromagnetic plunger. 2.) An automatic music selection tape recorder characterized in that when a first switch is opened at the same time as an operation button for the first switch is released, a muting transistor is maintained in an operating state through a Schmitt circuit for a charging time of the capacitor.