JPS6221162B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a cassette-type magnetic recording and reproducing machine that includes:
The present invention relates to a muting signal generating device for preventing impact noise, distorted sound, etc. generated when switching tape speeds during playback.

Recently, in cassette-type magnetic recording and reproducing machines (hereinafter referred to as cassette telecos), due to demands for expanding the dynamic range and improving the S/N ratio, the conventional 4.8
Similar to open-type magnetic recording/playback machines, tape speeds that were constant at cm/sec were now available with several tape speeds. In such cassette telecos, when the tape speed is changed during tape playback, unpleasant impact noises and distorted sounds occur until the tape speed stabilizes, and in particularly severe cases, speakers may be damaged. It was hot.

The present invention has been made in view of the above points, and provides a device for generating a muting signal for preventing unpleasant impact sounds and distorted sounds until the tape speed is stabilized.

Hereinafter, the present invention will be explained in detail based on one embodiment with reference to the drawings.

That is, FIG. 1 is a circuit diagram of the present invention, in which 1 is a preamplifier, 2 is a main amplifier, and 3 is a circuit diagram of the present invention.
is a muting short-circuit transistor (hereinafter referred to as a transistor) installed between the signal transmission line connecting the preamplifier 1 and the main amplifier 2 and the ground.
), 6 is a DC power supply, 7 is a control Tr connected in series via a resistor 4 between the DC power supply 6 and the base of the mutating short-circuit Tr 3, and 8 is a connection between the base of the control Tr 7 and the ground. a first switching Tr arranged in series with a resistor 10 in between;
9 is a resistor disposed between the emitter of the control Tr 7 and the collector of the first switching Tr 8; 11 is the second switching Tr; 12 and 1;
5 is the DC power supply 6 and the first switching Tr 8
first and second series circuits each including capacitors 13, 16 and resistors 14, 17 in parallel with the base of the circuit; The series circuit 15 is set larger. Further, the first switching Tr
A resistor 18 and a diode 19 for preventing malfunctions are arranged in parallel between the base of 8 and the ground. Capacitor 13 of the first series circuit 12
A tape speed switch 10 is connected via a resistor 20 between the connection point between the resistor 14 and the DC power supply 6.
1 (shown in FIG. 2), a switching type first timing switch 21 and a recording/playback changeover switch 22 are provided. In addition, 23
is a second switch 102 (shown in FIG. 2) that switches from playback to fast-forward FF or rewind REW.
The timing switch and the recording/playback changeover switch 22 are shown in the figure during playback.
5 and 24 are bias resistors, 25 and 26 are diodes, and 27 is a capacitor.

FIG. 2 is a tape speed control connection diagram showing a tape speed switch 101 and a switch 102 for switching from the playback state to fast-forward FF or rewind REW, both of which are related to the above-mentioned muting signal generator.

In the muting signal generator configured as described above, during the playback operation of the cassette telephony, the first and second switching transistors 8 and 11 and the control
All Tr7 are off, and the first and second
capacitors 13, 16 in series circuits 12, 15
is in a charged state.

In this state, when the tape speed switch 101 is operated to switch the tape speed, the first timing switch 21 of the switching type that is interlocked with the tape speed switch 101 is operated, and the timing switch 21 is temporarily switched between a and b during the switching operation. The terminals are shorted. At this time, the DC voltage applied from the DC power supply 6 causes the first switching Tr8 to
is turned on. Note that the timing switch 2
If the first shooting time is short, the first shooting time is short.
and capacitor 1 of second series circuit 12, 15
Even after the timing switch 21 is turned off, the first switching is continued by using the charging current of the timing switch 21.
The base potential of Tr8 is kept high for a certain period of time, and the first
Switching Tr8 is turned on for a desired time. Thus, when the switch 101 is operated, a stable muting signal is generated from the collector of the control Tr7. Also, tape speed switch 1
The above-mentioned operation can also be achieved by a second timing switch 23 that operates in conjunction with a switch 102 (shown in FIG. 2) that switches from the playback state to fast-forward FF or rewind REW, which is disposed in parallel with the switch 21 that operates in conjunction with Similarly, impact noise caused by switching can be prevented.

Furthermore, in the muting signal generator of the present invention, when the power switch (not shown) of the cassette television is turned off, the second switching Tr11
The first switching Tr 8 is turned on by the discharging action of the capacitor 27 connected to the emitter of the Tr 8, and a muting signal similar to that described above can be output. Furthermore, when the power switch is turned on, the first switching Tr8 is turned on by the current flowing through the second series circuit 15, resulting in the same operation as described above.

According to the present invention, the second series circuit,
Since the control transistor and the first switching transistor are used to generate muting signals when changing the tape playback speed and when the power switch is turned off, the configuration is simple and the muting signal can be generated under different conditions and timings when changing the tape playback speed and when the power switch is turned off. This has a practical effect of being able to reliably prevent unpleasant impact sounds and distorted sounds until the tape speed becomes stable.

In addition, although the mutating signal generated in this embodiment is supplied to the muting short circuit Tr3 disposed between the preamplifier 1 and the main amplifier 2, the same effect can be obtained even if the mutating signal is supplied to a signal transmission line other than the one described above. This is something to look forward to.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an embodiment of a muting signal generator according to the present invention, and FIG. 2 is a connection diagram of a switch related to FIG. 1. DESCRIPTION OF SYMBOLS 1... Preamplifier, 2... Main amplifier, 3... Muting short-circuit transistor, 6... DC power supply, 7... Control transistor, 8, 11... Switching transistor, 12, 15... Series circuit, 21...Timing switch, 101...Tape speed switching device.

Claims (1)

[Claims] 1. A DC power source, a control transistor that outputs a muting signal, a power switch connected between the control transistor and the DC power source, and a first switching circuit connected between the base of the control transistor and ground. a first series circuit including a transistor, a capacitor and a resistor connected in series between the base of the first switching transistor and the power switch; and a first series circuit connected in parallel to the capacitor of the first series circuit. a switching type timing switch interlocked with a tape playback speed switch; a second series circuit comprising a capacitor and a resistor connected in parallel to the first series circuit; a second switching transistor connected between the base of the switching transistor and a capacitor connected between the emitter of the second switching transistor and ground; A muting signal generating device characterized in that a muting signal is generated when a switch is turned off.