JPH0316082Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Technical field The present invention relates to a tape recorder, and particularly to a recording/playback switching circuit that switches between recording operation and playback operation. (B) Background Art A tape recorder has a recording function for recording signals on a magnetic tape and a playback function for playing back signals recorded on the magnetic tape. Tape recorders equipped with such dual functions, particularly cassette-type tape recorders that use tapes called cassettes, generally use a dual-purpose recording/playback magnetic head that performs both recording and playback operations. Tape recorders using such a magnetic head for recording and playback used a multi-circuit switch to switch between recording and playback operations, but recently a switch with a small number of circuits has been used to switch between recording and playback operations. An electronic switching system has been developed using (c) Purpose of the invention The present invention aims to provide a switching circuit suitable for a recording/playback switching circuit that electronically switches between recording and playback operations. (d) Embodiment of the invention The illustrated circuit is an embodiment of the recording/playback switching circuit of the invention. In the figure, 1 is a recording/playback magnetic head that operates as a recording head during recording and as a playback head during playback; 2;
is a tape recorder circuit in which a playback amplifier circuit, a recording amplifier circuit, a main amplifier circuit, a microphone amplifier circuit, etc. are incorporated, and there is an input terminal 3 into which the recording signal is input, and an input terminal 3 where the playback signal or monitor signal is output. A first control terminal 5 controls a reproduction system amplifier circuit, and a second control terminal 6 controls a recording system amplifier circuit. In such a tape recorder circuit 2, when the first control terminal 5 is grounded, the reproduction system amplifier circuit becomes inactive, and when the second control terminal 6 is grounded, the recording system amplifier circuit becomes inactive. It is configured as follows. Reference numeral 7 designates a first recording/playback switch which is normally located at the illustrated playback position and is switched to the opposite recording position by a recording operation, and includes a playback side terminal 7 _P , a recording side terminal 7 _R , and a switching slider 7 It has a common terminal _7c connected to _S and a power supply line 8. Reference numeral 9 denotes a recording/playback switching circuit which outputs a control signal in response to switching of the first recording/playback switch 7 and switches the signal path of the tape recorder circuit 2 between a state for playback operation and a state for recording operation. It is. 10 is the first
This is a second recording/playback switching switch that is switched in conjunction with the recording/playback switching switch 7, and the playback side terminal 1
_0P , a recording side terminal _10R , a switching slider _10S , and a common terminal _10c connected to the power supply line 8. The second recording/playback switch 10 is
While the switching slider _10S is being displaced from the playback position to the recording position or from the recording position to the playback position by the switching operation, the switching slider _10S connects the playback side terminal _10P , the recording side terminal _10R , and the common terminal. This is a switching type switch in which _10c is short-circuited. Reference numeral 11 denotes a first time constant circuit connected between the recording side terminal 10R of the second recording/playback switch ₁₀ and ground, and is composed of resistors 12, 13 and a first capacitor 14. 1
5 is a first switching transistor whose collector is connected to the first control terminal 5 of the tape recorder circuit 2 and whose emitter is grounded;
It is connected to the charging side terminal of the capacitor 14. 17 is a second switching transistor whose collector is connected to the second control terminal 6 of the tape recorder circuit 2 and whose emitter is grounded; its base is connected to the power supply line 8 via a resistor 18; ing. 19 is the second
A third switching transistor whose collector is connected to the base of the switching transistor 17 and whose emitter is grounded,
Its base is connected via resistors 20 and 21 to the first
It is connected to the charging side terminal of the capacitor 14. A second time constant circuit 22 is connected between the charging side terminal of the first capacitor 14 and the ground, and is composed of a resistor 23 and a second capacitor 24. Reference numeral 25 denotes a bias oscillation circuit which becomes operational when the control terminal 26 is grounded, and is connected so that its output signal is applied to the recording/reproducing magnetic head 1. 27 is a fourth switching transistor whose collector is connected to the control terminal 26 of the bias oscillation circuit 25 and whose emitter is grounded, and whose base is connected to the charging side terminal of the second capacitor 24. . Reference numeral 28 has a base connected to the playback side terminal 10 of the second recording/playback switch 10 via a resistor 29.
A first control transistor whose emitter is connected to _P and whose emitter is grounded, and whose collector is connected to a resistor 12 constituting the first time constant circuit 11 .
and connection point A of 13. 30 is a second control transistor whose base is connected to the playback terminal _10P of the second recording/playback switch 10 via a resistor 31 and whose emitter is grounded; its collector is connected to the third switching switch 10; It is connected to a connection point B between resistors 20 and 21, which is connected to the base circuit of transistor 19. 32, the base is connected to the playback side terminal _10P of the second recording/playback switch 10 via the resistor 33.
and a third control transistor whose emitter is grounded, and whose collector is connected to the charging side terminal of the second capacitor 24 constituting the second time constant circuit 22 . As described above, the recording/reproduction switching circuit of the present invention is constructed, and its operation will be explained next. First, the case where the first recording/playback switch 7 and the second record/playback switch 10 are in the illustrated playback position will be described. The first recording/playback switch 7
When the tape recorder circuit 2 is at the playback position, the signal path of the tape recorder circuit 2 is in a state for playback operation in response to a control signal from the recording/playback switching circuit 9. Further, when the second recording/playback switch 10 is in the playback position, the first
The capacitor 14 and the second capacitor 24 constituting the second time constant circuit 22 are in a state where no charging current is supplied. Therefore, in this state, the first switching transistor 15, the third switching transistor 19 and the fourth switching transistor 27 are in a non-conducting state, and the second switching transistor 17 is in a conducting state. As a result, the amplifier circuit constituting the tape recorder circuit 2 is in a state of performing a reproduction operation, and the bias oscillation circuit 25 is in a non-operating state. A reproduction signal reproduced by the recording/reproducing magnetic head 1 is amplified by a reproduction amplifier circuit and a main amplifier circuit constituting a tape recorder circuit 2, and then output to an output terminal 4. Therefore, the user can listen to the reproduced signal through a speaker or the like connected to the output terminal 4. The playback operation is performed as described above, but next, a case will be described in which the first recording/playback switch 7 and the second record/playback switch 10 are in the recording position, which is opposite to the state shown in the figure. When the first recording/playback switching switch 7 is in the recording position, the signal path of the tape recorder circuit 2 is in a state for performing a recording operation in response to a control signal from the recording/playback switching circuit 9. Further, when the second recording/playback switch 10 is in the recording position, the recording side terminal 10 _R Since a charging current is supplied through the first capacitor 14 and the second capacitor 24, the first capacitor 14 and the second capacitor 24 are in a charged state. Therefore, in such a state, the first switching transistor 15,
The third switching transistor 19 and the fourth switching transistor 27 are in a conductive state, and the second switching transistor 17 is in a non-conductive state. As a result, tape recorder circuit 2
The amplifier circuit constituting the oscillation circuit 25 is in a recording operation state, and the bias oscillation circuit 25 is in an operating state. A recording signal from a microphone (not shown) inputted to the input terminal 3 is amplified by a microphone amplification circuit and a recording amplification circuit, and then, together with a bias signal from the bias oscillation circuit 25, a recording/playback magnetic field is generated. The signal is applied to head 1 and recorded on the magnetic tape. As described above, the reproduction operation and recording operation in this embodiment are performed, but next, the switching operation accompanying the recording operation will be explained. When the user performs a recording operation in the illustrated state, the first recording and playback switch 7 and the second recording and playback switch 10 are switched to the recording side, but the second recording and playback switch 10 is switched in the middle of the switch. child _10S , playback side terminal _10P , recording side terminal _10R and common terminal _10C
becomes short-circuited. In such a short-circuited state, power is supplied to the first time constant circuit 11 through the recording side terminal _10R , but a bias current is supplied to the base of the first control transistor 28 through the reproduction side terminal _10P , and the first control transistor 28 is supplied with bias current through the reproduction side terminal 10P. 28
is in a conductive state, the connection point A is grounded, and no charging current flows to the first capacitor 14. Furthermore, no charging current flows through the second capacitor 24 to which the charging current is supplied through the first time constant circuit 11 . Therefore, the first switching transistor 15, the third switching transistor 19, and the fourth switching transistor 27 are in a non-conducting state, and the second switching transistor 17 is in a conducting state, so that the tape recorder circuit 2 enters the recording operation state. The switching of the bias oscillation circuit 25 and the switching of the bias oscillation circuit 25 to the operating state are not performed. When the switching operation is performed further than the state in the middle of such switching, the switching slider 10S of the second recording/playback switching switch ₁₀ changes to the recording side terminal 1.
0 Move to _R side and connect playback side terminal 10 _P and common terminal 10
The short-circuit condition with _c is released. As a result, the playback side terminal _10P of the second recording/playback switch 10
The first control transistor 28, the second control transistor 30, and the third control transistor 32, which were in a conductive state due to the supply of bias current, are reversed to a non-conductive state. When the first control transistor 28 is reversed to a non-conducting state, the first capacitor 14 forming the first time constant circuit 11 and the second time constant circuit 22 are formed through the recording side terminal _10R of the second recording/playback switch 10. A charging current is supplied to the second capacitor 24. Said second
Since the charging current is supplied to the capacitor 24 through the first time constant circuit 11 , the rise in the charging potential of the second capacitor 24 is slower than the rise in the charging potential of the first capacitor 14. When a predetermined period of time elapses after the charging operation of the first capacitor 14 is started, the charging potential of the first capacitor 14 rises to a predetermined potential. When the charging potential of the first capacitor 14 rises to a predetermined potential, the first switching transistor 15 and the third switching transistor 19 are turned on, and the second switching transistor 17 is turned on.
is reversed to non-conducting state. As a result, the amplifier circuit constituting the tape recorder circuit 2 enters a state in which it performs a recording operation. After a predetermined period of time has elapsed after such an operation, the second time constant circuit 22
The charging voltage of the capacitor 24 rises to a predetermined potential, and the fourth switching transistor 27 is turned on. When the fourth switching transistor 27 is turned on, the bias oscillation circuit 25 becomes active, and the tape recorder enters the recording operation state described above. As explained above, when the recording operation is performed from the playback state, the switching operation is performed.
When the switch is in the middle of switching, the first control transistor 28 is turned on to prevent switching to the recording mode, and a predetermined period of time after the second recording/playback switch 10 is switched to the recording mode. Tape recorder circuit 2 and bias oscillation circuit 25
is switched to the operating state for recording, so even if the user presses and holds the record button for a long time between the playback position and the recording position, the signal path is switched to the recording state by the first recording/playback switch 7. After the operation is performed, the amplifier circuit is switched to the recording state, and then the bias oscillation circuit 25 is put into the operating state, so that it is possible to suppress as much as possible the noise generated at the time of switching from being recorded on the magnetic tape. I can do it. As described above, the switching operation from the playback state to the recording state is performed, but next, the operation when canceling the recording state by a stop operation or the like will be explained. If a stop operation is performed while the recording operation is in progress, the first recording/playback switch 7 and the second record/playback switch 10 are switched from the recording position to the playback position.
When the switching slider _10S of the second recording/playback switch 10 is displaced from the recording position to the playback position, the playback side terminal _10P , the recording side terminal _10R , and the common terminal _10c are temporarily short-circuited in the middle. However, since the recording button is not operated at the time of such switching, the switching slider _10S is not held in the mid-switching state, but is immediately displaced to the playback side. When the playback side terminal _10P is short-circuited to the common terminal _10c due to the displacement of the changeover slider _10S of the second recording/playback changeover switch 10, the first control transistor 28 and the second control transistor 28, which were in a non-conducting state, are in a non-conducting state. Transistor 30 and third control transistor 32 are reversed to a conductive state. When the second control transistor 30 is turned conductive, the third switching transistor 19 is immediately turned non-conductive and the second switching transistor 17 is turned conductive. The system amplifier circuit becomes inactive. Further, when the third control transistor 32 is reversed to a conductive state, the charge stored in the second capacitor 24 constituting the second time constant circuit 22 is instantly discharged, and the fourth switching transistor 27 is reversed to a non-conductive state. As a result, the bias oscillation circuit 25 becomes inactive. In this way, as the first control transistor 28, the second control transistor 30, and the third control transistor 32 are inverted to the conducting state, the second switching transistor 17, the third switching transistor 19, and the fourth switching transistor 27 are turned on. The inversion operation of the first switching transistor 15 is immediately performed, but the inversion operation of the first switching transistor 15 to the non-conducting state is performed immediately after the first capacitor 14
This delay is caused by a predetermined time delay due to the charge that was previously stored. As a result, the reproduction system amplifier circuit constituting the tape recorder circuit 2 becomes operational after the recording system amplifier circuit and bias oscillation circuit 25 are rendered inactive. Therefore, it is possible to prevent noise generated when the recording system amplifier circuit and bias oscillation circuit 25 become inactive from being output to the output terminal 4. Furthermore, since the operation of the bias oscillation circuit 25 is immediately stopped when the recording operation is canceled, the problem of erasing the signal recorded on the magnetic tape when switching from the recording state to the playback state by a review operation, etc. is avoided. It will never occur. (E) Application example of the invention In this embodiment, the switching circuit that controls the operation of the tape recorder circuit 2 and the operation of the bias oscillation circuit 25 is connected to the first switching transistor 1.
5, second switching transistor 17, third
It is composed of a switching transistor 19 and a fourth switching transistor 27, but it is PNP.
It can also be constructed using a type transistor or other switching elements. Further, a control transistor 2 controls the charging operation of the first capacitor 14 and the second capacitor 24 that constitute the first time constant circuit 11 and the second time constant circuit 22.
Although NPN type transistors were used as 8 and 32, PNP type transistors can also be used. (f) Effect The present invention uses a switching type switch in which the playback side terminal and the recording side terminal are short-circuited in the middle of switching, as a recording/playback changeover switch for switching between the recording operation and the playback operation of a tape recorder. Utilizing the characteristics of the switch, the switching of the amplifier circuit to the recording operation state is made slower than the switching of the signal path, regardless of the length of the switching operation time of the recording button, and the current is supplied through the first time constant circuit. Since the start of operation of the bias oscillation circuit is delayed by the second time constant circuit, it is possible to suppress the noise at the time of switching from being recorded on the magnetic tape.
The present invention is extremely effective when applied to a tape recorder in which the recording/playback switching operation is performed electronically.

[Brief explanation of the drawing]

The illustrated circuit is an embodiment of the recording/playback switching circuit of the present invention. Explanation of main drawing numbers, 1...Magnetic head for both recording and playback, 2...Tape recorder circuit, 7...First recording and playback switching switch, 9...Recording and playback switching circuit,
10...Second recording/playback selector switch, 11 ...First time constant circuit, 14...First capacitor, 15
...First switching transistor, 17...
2nd switching transistor, 19...3rd
Switching transistor, 22 ... Second time constant circuit, 24... Second capacitor, 25... Bias oscillation circuit, 27... Fourth switching transistor, 28... First control transistor,
30...second control transistor, 32...third
control transistor.

Claims (1)

[Scope of utility model registration request] In a tape recorder configured to electronically switch between a recording operation and a playback operation, there is a first switch that switches from a playback position to a recording position during a recording operation and also switches a signal path of the tape recorder circuit from a playback operation state to a recording operation state. a recording/playback changeover switch; a second recording/playback changeover switch of a switching type that is switched in conjunction with the first recording/playback changeover switch and short-circuits a playback side terminal and a recording side terminal during the switching; and the second recording/playback changeover switch. a first time constant circuit including a first capacitor that is charged when the recording/playback selector switch is in the recording position; a second time constant circuit including a second capacitor that is charged by the current from the first time constant circuit; a switching circuit that switches an amplifier circuit of the tape recorder circuit from a playback operation state to a recording operation state when the charging potential of the first capacitor rises to a predetermined value or more;
a switching transistor that activates the bias oscillation circuit when the charged potential of the second capacitor rises to a predetermined value or more; and a switching transistor that activates the bias oscillation circuit when the charging potential of the second capacitor rises to a predetermined value or more; a first control transistor that conducts when the first time constant circuit is short-circuited and prevents the charging operation of the first capacitor constituting the first time constant circuit; A recording/reproduction switching circuit for a tape recorder, comprising a second control transistor that conducts when a side terminal and a recording side terminal are in a short-circuited state and short-circuits both ends of a second capacitor constituting the second time constant circuit.