JPS6235Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape recorder that detects a non-signal portion existing between each of a plurality of recording signal areas on a magnetic tape. Recently, tapes that have no-signal areas between each of a plurality of recorded signal areas, such as music tapes that have no-signal areas between songs, can be fast-forwarded or rewound at high speed to remove those no-signal areas. Tape recorders that automatically start playing from the beginning of the next song upon detection are becoming popular. In particular, the present invention includes means such as a plunger that generates a single pulse from a gate circuit when a non-signal portion of the tape is detected by fast speeding up or rewinding, and switches the operation mode of the tape drive mechanism by the output of this single pulse. This is designed to prevent the plunger from malfunctioning due to a single pulse being accidentally generated from the gate circuit immediately after the power is turned on in the tape recorder being operated. The detection device will be explained. Detection heads 1 and 1' detect the presence or absence of a recording signal, and these heads are also used as recording and reproducing heads. These detection heads 1 and 1' detect the presence or absence of recorded signals in the left and right channels of the stereo tape 2, and are located at the positions where they touch the tape when the playback button is locked and the fast forward or rewind button is locked. . 3, 3' are the detection heads 1,
a first amplifier that amplifies the minute signal detected by 1';
4-1, 4-2 and 5-1, 5-2 are switches that are closed in conjunction with fast-forwarding and rewinding operations, respectively; switches 4-1, 4-2 are closed during fast-forwarding.
is closed, and switches 5-1 and 5-2 are activated during rewinding.
is closed, and the outputs of the first amplifiers 3, 3' are applied to the second amplifier 6 at the next stage. 7 is each of the switches 4-1, 4-2, 5-1,
A reproduced signal attenuation resistor is connected between the common connection point 5-2 and ground, and the amount of the signal input to the second amplifier 6 is adjusted by this resistor 7. The second amplifier 6 is composed of transistors 8 and 9, and its signal output is connected to a capacitor 1.
0 to the base of switching transistor 11. The switching transistor 1
1 indicates the presence or absence of a signal at a high DC potential (high level)
or convert it to a lower potential (low level). 12
is the collector of the switching transistor 11.
Capacitor 1 connected to power supply via emitter
3 and a charging/discharging circuit consisting of resistors 14 and 15, 1
6 and 17 are inverters that invert the output in response to the charging and discharging levels of the charging/discharging circuit 12 ; 18 is an integrating circuit consisting of a resistor 19 and a capacitor 20 connected to the output terminal of the inverter 16; 21 is an inverter of the inverter 17; A first input a receiving the output is at a low level and a second input b receiving the integrated output of the integrating circuit 18 .
3 inputs that generate a single pulse of a constant width when is at a low level and the third input c is also at a low level.
NOR gate circuit; 22 is the NOR gate circuit 2;
The drive circuit drives the plunger 25 by making the transistors 23 and 24 conductive by a single pulse generated by the drive circuit 1, and the plunger 25 is operated to switch the operation mode of the tape drive mechanism. Reference numeral 26 denotes a manual selection switch connected to the drive circuit 22 , which disables the operation of the drive circuit 22 when it is closed. A resistor 27 is connected to the third input c of the NOR gate circuit 21, and the other end of this resistor 27 is connected to a capacitor 28 connected in series between the power supply line and the ground.
and the connection midpoint of the resistor 29. 30 is a power switch connected to the power line. Although the present invention is constructed as described above,
In order to facilitate understanding of the operation of the logic circuit portion of the present invention, FIG. 2 shows a conventional logic circuit portion, and FIG. 3 shows a logic circuit portion of the present invention. Now, when the power switch 30 is open, the second
In the conventional circuit shown in the figure, since no charge is accumulated in the capacitor 20, immediately after the power switch 30 is closed, if the input of the inverter 16 is at a low level, its output becomes a high level, forming an integrating circuit 18 . Although current flows through the capacitor 20,
The second input b of the NOR gate circuit 21 remains at a low level for a certain period of time, while the output of the inverter 17 becomes a low level and the first input of the NOR gate circuit 21
Since the input a is set to a low level, the output of the NOR gate circuit 21 eventually becomes a high level and generates a single pulse to operate the plunger 25 shown in FIG. On the other hand, even in the circuit of the present invention shown in FIG. 3, when the power switch 30 is open, the capacitor 2
and 28, and immediately after the power switch 30 is closed, the first input a and the second input b of the NOR gate circuit 21 are at a low level for a certain period of time, as in FIG. By closing the switch 30, a charging current flows through the capacitor 28, and the resistor 2
9 rises, and the third input c of the NOR gate circuit 21 is brought to a high level through the resistor 27. As a result, the second input b of the NOR gate circuit 21
The third input c is at a high level until it becomes high level due to charging of the integrating capacitor 20, and then when the capacitor 28 is completely charged, the third input c becomes a low level, so the power switch 30 A single pulse is no longer generated from the NOR gate circuit 21 immediately after the input of the signal. Since the logic circuit of the present invention operates in this manner, the operation of the device of the present invention will be explained below with reference to FIG. When detecting a no-signal portion between songs on a music tape by fast forwarding or rewinding the tape to locate the beginning of the song and automatically play the song from the beginning, first release the selection switch 26. drive circuit
22 is placed in an operation standby state, and the play button and fast forward button, or the play button and rewind button of the tape recorder are pressed to lock each button. In this state, the music tape is fast forwarded or rewound at high speed while in contact with the detection heads 1, 1'. Now, if the detection heads 1, 1' are facing the recorded signal portion on the magnetic tape, the detection heads 1, 1'
The reproduced signal detected at 1' is transmitted to the first amplifier 3,
3', switch 4-1, 4-2, or 5-1, 5
A part of the signal is attenuated by the signal attenuation resistor 7 and applied to the second amplifier 6 through -2. The output of this amplifier 6 is applied to the base of a switching transistor 11 through a capacitor 10.
When the base potential exceeds V _BE (approximately 0.6V) of the transistor 11, the collector potential of the transistor 11, that is, the potential of the terminal A of the charging/discharging circuit 12 , becomes close to V _CC as the transistor 11 turns on and the base potential increases. When VBE is lower than _VBE , the transistor 11 is turned off and becomes the ground potential. Therefore, when there is a reproduced signal, the potential at terminal A is high level, and when there is no reproduced signal, the potential at terminal A is low level. The charging/discharging circuit 1 is activated by turning on the switching transistor 11 due to the presence of the reproduction signal.
The capacitor 13 of No. 2 is charged. Therefore, since the inverters 16 and 17 constitute a Schmitt trigger circuit, the waveform of the voltage at terminal A is shaped, and the voltage at terminal A changes from a high level to a low level due to a change from presence to absence of a reproduction signal. is detected when the output of the inverter 17 changes from a high level to a low level. When there is a reproduction signal, the first input a of the NOR gate circuit 21 is at a high level, the second input b is at a low level, and the output is at a low level, so the drive circuit 22 does not operate and the plunger 25 It doesn't work. When the inter-track no-signal portion on the magnetic tape 2 faces the detection heads 1, 1', there is no reproduction signal from the detection heads 1, 1', so the switching transistor 11 is turned off. After a period of time determined by the charging/discharging circuit 12 has elapsed, the output of the inverter 17, that is, the first input a of the NOR gate circuit 21 changes from high level to low level. However, the second input 5 of the NOR gate circuit 21 does not go from a low level to a high level immediately due to the integration circuit 18 made up of a resistor 19 and a capacitor 20, but changes to a high level after a delay of a time constant due to the resistor 19 and capacitor 20. Become. Therefore, since the third input c of the NOR gate circuit 21 is also at a low level, there will be a time when all three inputs are at a low level, and only during this time will the NOR gate circuit 21 be at a low level.
The output of the gate circuit 21 becomes high level. After the state in which the reproduction signal is present changes to the state in which there is no reproduced signal, the transistor 2 of the drive circuit 22 is closed for a time constant determined by the resistor 19 of the integrating circuit 18 and the capacitor 20.
3 and 24, and the plunger 25 is activated. Due to the operation of the plunger 25, the fast forward button or rewind button, which was previously locked together with the playback button, is unlocked, and only the playback button is locked, and the magnetic tape is in a playback state with the non-signal portion at the beginning. The mode will be switched to . In the present invention, which operates as described above, the capacitor 10 connected to the base of the switching transistor 11 can function as a low frequency cutting capacitor by changing its value. In other words, when recording from a record to magnetic tape, a hum component may be recorded between songs, and since the undesired signal of this hum component has a low frequency,
There are no audible problems during normal playback, but when the tape is running at high speed and detecting no-signal areas, the playback level is adjusted to match the high-speed playback.
The frequency also increases, and even between songs containing hum components, the state becomes the same as when there is a signal, resulting in a malfunction in which the song is skipped. To prevent this, use a low frequency (e.g. 100
Hz) by selecting the value of the capacitor 10, so that only frequencies above a certain level can be accompanied as a signal. In addition, the capacitor 13 of the charging/discharging circuit 12 maintains the terminal voltage of the charging/discharging circuit 12 even if the level of the reproduction signal momentarily drops during high-speed playback of a song.
If no signal continues for a certain period of time, the subsequent Schmitt trigger circuit will not operate. Furthermore, the resistor 7 connected to the input side of the amplifier is
It is useful for attenuating the squealing sound of the reproduced signal during high-speed reproduction without adding a special electronic circuit, and is used for sensitivity adjustment. As described above, according to the no-signal detection device for the tape recorder of the present invention, when a no-signal portion of the tape is detected, a single pulse signal is generated from the NOR gate circuit, and the plunger for mechanism switching is activated for the duration of this pulse signal. Since the start of the song can be obtained by energizing the plunger, there is no need for a complicated switch circuit to release the energization of the plunger, which simplifies the circuit configuration and allows current to flow continuously through the plunger. It is possible to improve safety by eliminating the need for each inverter and NOR gate circuit to generate a single pulse signal.
Since it can be formed using a CMOS integrated circuit or the like, automatic tape selection can be performed safely and reliably even when the output of the detection circuit fluctuates due to fluctuations in the DC power supply. According to the device of the present invention, there is no fear that a single pulse will be generated by mistake from the NOR gate circuit immediately after the power switch is turned on, so the plunger will not malfunction and is of high practical value.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of the device of the present invention, FIG. 2 is a conventional logic circuit, and FIG. 3 is a logic circuit of the present invention. 1, 1'...detection head, 2...magnetic tape,
3, 3', 6...Amplifier, 4-1, 4-2, 5-
1,5-2...Switch, 7...Resistance, 10...
Capacitor, 11... Switching transistor, 12 ... Charge/discharge circuit, 16, 17... Inverter, 18 ... Integrating circuit, 21... 3-input NOR
Gate circuit, 22 ... Drive circuit, 25... Plunger, 28... Capacitor.

Claims (1)

[Scope of utility model registration request] In a device for detecting a non-signal portion existing between each of a plurality of recording signal areas on a magnetic tape,
A detection head that detects the presence or absence of the recorded signal, an amplifier that amplifies the reproduced signal detected by the detection head, a switching transistor connected to the output side of the amplifier, and a collector-emitter of the switching transistor. a Schmitt trigger circuit consisting of a charge/discharge circuit connected to a power source, a first inverter connected to a signal output terminal of the charge/discharge circuit, and a second inverter connected to the inverter; A third input terminal is connected to the first input terminal, a second input terminal is connected to the connection point of the first and second inverters via a resistor, and a third input terminal is connected to a high level for a certain period of time when the power switch is turned on. Has 3 inputs
A NOR gate circuit is provided between the second input terminal and the ground point, and when the reproduction signal is lost and the switching transistor is turned off, the
It consists of a capacitor that is combined with the resistor to form an integral circuit in order to output a single pulse signal from the NOR gate circuit, and a plunger for mechanism switching that is energized and controlled by the pulse signal. A non-signal portion detection device for a tape recorder, which is characterized by preventing the generation of pulse signals.