JPS634241B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a tape recorder, and will be described in detail below with reference to the illustrated embodiments.

In the figure, 1 is a playback head that plays back signals recorded on a magnetic tape, and 2 is the playback head 1.
3 is an electronic volume that electronically adjusts the level of the signal amplified by the reproduction amplifier circuit 2, and an input terminal 4, an output terminal 5, and a control It is equipped with a terminal 6. 7 is a microphone amplifier circuit for amplifying the signal obtained from the microphone 8; 9 is a variable resistor for adjusting the level of the output signal of the microphone amplifier circuit 7; 10 is a variable resistor 9;
This is an electronic switch that controls the output of a signal whose level has been adjusted by the input terminal 11 and the output terminal 1.
2 and a control terminal 13. 14 is a main amplifier circuit whose input terminals are connected to the output terminal 5 of the electronic volume 3 and the output terminal 12 of the electronic switch 10, and a speaker 15 is connected as a load. 16 is a clock pulse generation circuit that generates clock pulses; 17 is a frequency division circuit that divides the frequency of the pulse signal from the clock pulse generation circuit 16; 18 is an adjustment circuit that adjusts the division ratio of the frequency division circuit 17; An AND circuit to which the signal frequency-divided by the frequency circuit 17 is input; 20 is the AND circuit;
The input terminal 21 is connected to the output terminal of the circuit 19, and the counter circuit performs a counting operation when the reset terminal 22 is at L (low) level. 23 is a manually operated and lock type control switch; one terminal 23a
is grounded, and the other terminal 23b is connected to the reset terminal 22 of the counter circuit 20 and to the power supply via a resistor 24. 2
A DA converter 5 converts the digital signal output from the counter circuit 20 into an analog signal, and its output terminal is connected to a control terminal 6 to control the operation of the electronic volume 3. 2
6 is a control circuit that outputs an H (high) level switching signal when the count number of the counter circuit 20 reaches a predetermined value, and its output terminal 27 is connected to the control terminal 13 of the electronic switch 10 and the inverter 2.
8 to the input terminal of the AND circuit 19. Reference numeral 29 denotes a setting circuit for setting the count number at which the switching signal is output from the control circuit 26. In such a circuit, electronic volume 3
is configured such that as the signal applied to the control terminal 6 becomes larger, the amount of attenuation becomes larger, that is, the level of the signal outputted to the output terminal 5 becomes smaller. In addition, the electronic switch 10 has a control terminal 1
When the signal applied to No. 3 is at L level, it is turned off, and when it is at H level, it is turned on.

The present invention is constructed as described above, and its operation will be explained next. When the control switch 23 is in the open state shown, an H level signal is applied to the reset terminal 22 of the counter circuit 20, so the counter circuit 20 is in an inactive state. Further, the output of the control circuit 26 is at the L level, and the electronic switch 10 is in the off state. In such a state, when the user performs a playback operation, the tape recorder enters the playback operation state, and the playback head 1
A signal such as music recorded on a magnetic tape is played back. The signal reproduced by the reproduction head 1 is input to a reproduction amplifier circuit 2, amplified, and then applied to an input terminal 4 of an electronic volume 3. The reproduction signal applied to the input terminal 4 of the electronic volume 3 is outputted to the output terminal 5 after its level is adjusted by the electronic volume 3 whose attenuation amount is set by an adjustment means (not shown). The output terminal 5
The reproduced signal output from the main amplifier circuit 14 is input to the main amplifier circuit 14, amplified, and then applied to the speaker 15 to emit sound. In such a reproduction state, AND circuit 1
A pulse signal is output from the output terminal of the counter circuit 9, but since the counter circuit 20 is in an inactive state, the pulse signal is not counted, and no count signal is output from the output terminal. Further, since the electronic switch 10 is in the off state, the signal from the microphone 8 is not applied to the main amplifier circuit 14.

The playback operation is performed as described above, but when the control switch 23 is closed while the tape recorder is in the playback state, the reset terminal 22 of the counter circuit 20 is grounded. Then, the counter circuit 20 starts counting operation.
When the counter circuit 20 starts counting, a digital signal corresponding to the counted number is output from its output terminal. The digital signal, which is the output signal of the counter circuit 20, is converted into an analog signal by the DA converter 25 and sent to the electronic volume 3.
is applied to the control terminal 6 of. The level of the analog signal applied to the control terminal 6 of the electronic volume 3 gradually increases as the number of pulse signals counted by the counter circuit 20 increases, so that the amount of attenuation caused by the electronic volume 3 increases. It gradually becomes larger. Therefore, the level of the reproduction signal output to the output terminal 5 of the electronic volume 3 gradually decreases. When the count number of the counter circuit 20 reaches the value set by the setting circuit 29, the control circuit 26 outputs an H level signal which is a switching signal. When the control circuit 26 outputs an H level signal, one input signal of the AND circuit 19 becomes L level, so the counter circuit 2
The pulse signal input to 0 disappears. Therefore, the count number of the counter circuit 20 does not increase any further, and the reduction in the level of the reproduced signal by the electronic volume 3 stops. Further, when an H level signal is output from the control circuit 26, the H level signal is applied to the control terminal 13 and the electronic switch 10 is turned on. Therefore, the signal from the microphone 8 is transmitted to the microphone amplifier circuit 7-
After being input to the main amplifier circuit 14 through the variable resistor 9 and electronic switch 10 and amplified, the speaker 1
The sound is emitted from 5. In this way, when the control switch 23 is switched while the tape recorder is in the playback state, the volume of the playback signal emitted from the speaker 15 gradually decreases, and when the volume reaches the set value, the signal from the microphone 8 is output. is now emitted from the speaker 15.

When the control switch 23 is opened in such a state, the reset terminal 22 of the counter circuit 20 is reset.
Since an H level signal is applied to the counter circuit 20, the counter circuit 20 is reset to the initial state. When the counter circuit 20 is reset, its output becomes the initial state, so that the control terminal 6 of the electronic volume 3
The signal applied to the electronic volume 3 disappears, and the electronic volume 3
returns to its original state. Further, since the output of the control circuit 26 is inverted to the L level, the electronic switch 10 is turned off, and the signal from the microphone 8 is cut off, so that only the reproduced signal is emitted from the speaker 15.

In such a circuit, by changing the set value of the setting circuit 29, the amount of reduction in the level of the reproduced signal by the electronic volume 3 can be set arbitrarily, and the frequency dividing ratio of the frequency dividing circuit 17 can be varied by the adjusting circuit 18. In this way, the speed at which the level of the reproduced signal is lowered by the electronic volume 3 can be freely varied. Furthermore, although the case has been described in which an electronic switch is used as a means for switching the signal from the microphone 8, a relay or the like may also be used.

As explained above, when the control switch of the present invention is switched while the tape recorder is in the playback state, the control circuit gradually reduces the volume of the sound played from the magnetic tape, and then main amplifies the signal from the microphone. Since it is led to the circuit, it is convenient when giving a speech at a wedding banquet, for example.

[Brief explanation of the drawing]

The illustrated circuit is one embodiment of the control circuit of the present invention. Explanation of main figure numbers, 1...Reproduction head, 3...Electronic volume, 8...Microphone, 10...Electronic switch, 14...Main amplifier circuit, 16...Clock pulse generation circuit, 17...Frequency division Circuit, 20...
... Counter circuit, 23 ... Control switch, 25
...D-A converter, 26 ... Control circuit, 29 ...
Setting circuit.

Claims (1)

[Claims] 1. In a tape recorder equipped with a playback circuit including a playback head that plays back signals recorded on a magnetic tape and a microphone circuit that amplifies signals from a microphone, a clock pulse generation circuit that generates clock pulses and the clock pulse a frequency divider circuit that divides the frequency of the pulse signal from the generator circuit; a control switch that is manually switched; and a counter circuit that enters a counting operation state by switching the control switch and counts the pulse signal from the frequency divider circuit; a D-A converter that converts the digital signal that is the output signal of the counter circuit into an analog signal; and a D-A converter that is controlled by the signal from the D-A converter and adjusts the level of the playback signal from the playback system circuit. an electronic volume; a main amplifier circuit into which a signal whose level has been adjusted by the electronic volume is input; a control circuit that outputs a switching signal when the count of the counter circuit reaches a set value; and switching from the control circuit. The switching means operates when a signal is applied and guides the signal from the microphone system circuit to the main amplifier circuit, and after gradually lowering the level of the reproduced signal from the magnetic tape by switching the control switch. A control circuit for a tape recorder, characterized in that a signal from the microphone is guided to a main amplifier circuit.