JPH0648581Y2 - Cue signal recording circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a cue signal recording circuit for recording a cue signal on a magnetic tape by a full width erasing head whose impedance is converted in a magnetic recording / reproducing apparatus. is there.

(B) Conventional technology Conventionally, as a technology for recording a cueing signal on a magnetic tape with a full-width erasing head whose impedance is converted, for example, "SCHEMATIC DIAGRAM & PRINTED CIRCUIT BOARD" of FVH-730, which is VIDEO CASSETTE RECORDER from FISHER, No. 4 The circuit of the page is presented.

FIG. 2 shows the circuit, and when the figure number and the configuration are described, (1) is a power supply terminal to which a power supply voltage for operating an oscillation circuit described later is input, and (2) is a base and a collector of which are primary. A transistor which is connected to both ends of the coil (3) and whose emitter is grounded through the resistor (4),
(5) is a coil connected to the power supply terminal (1) and the collector of the transistor (2), (6) is a secondary coil,
One end of (7) is a capacitor (8) as its load.
And a voice head which is connected to one end of the secondary coil (6) through a resistor (9) and whose other end is grounded,
(10) is a voice erasing head having one end connected to an arbitrary point of the secondary coil (6) and the other end grounded, and (11) has one end other than the secondary coil (6). A full-width erase head, which is connected to one end and the other end is grounded via a coil (12), has both ends connected to the arbitrary one point and the other end of the secondary coil (6), A capacitor that forms a resonance circuit with the secondary coil (6) to determine the oscillation frequency, (14) an audio terminal to which an audio signal is input, (15) one end of the audio head (7) and an audio terminal ( An amplifier connected between 14), (16) a power supply terminal to which a power supply voltage is input, and (17) a base of which is connected to the power supply terminal (16) through a resistor (18) and its collector. Is connected to the other end of the full width erasing head (11) and its emitter is connected. Is, the impedance transistor for varying the full-width erasing head (11), (19) a control signal (e.g., 30Hz cueing signal recording
Input terminal (20), whose base is connected to the input terminal (19) through a resistor (21) and whose collector is connected to the base of the transistor (17). A transistor whose emitter is grounded, (22) is an input terminal to which a control signal for switching the transistor (20) is input, (23)
Has its base through the resistor (24) through the input terminal (22)
The transistor (25) is a magnetic tape whose collector is connected to the base of the transistor (20) and whose emitter is grounded. The oscillation circuit (26) for AC bias recording is composed of the elements shown by the alternate long and short dash line.

(C) Problems to be solved by the device Therefore, the transistors (17) (20) (23) and the oscillation circuit (26) are operated to obtain the erase current of the full width erase head (11), that is, FIG. When the cue signal shown in Fig. 3 (a) synchronized with the control signal for recording the cue signal shown in (b) is recorded on the magnetic tape (25), the counter coil synchronized with the control signal is generated in the secondary coil (6). Electric power is generated, in other words, the current flowing through the secondary coil (6) changes, and the erasing current of the voice erasing head (10) is the same as that in FIG. 3 (b). The differential waveform synchronized with the control signal was generated. As a result, the differential waveform is recorded on the magnetic tape (25) and is reproduced as noise by the audio head (7).

(D) Means for Solving the Problems The present invention has been made to solve the above problems, and has a full width in which its impedance is varied by a switching element to which a control signal for recording a cue signal is input. In a magnetic recording / reproducing apparatus for recording a cueing signal on a magnetic tape by an erasing head, an AC bias recording for connecting the voice erasing head and the full width erasing head and its secondary coil at the time of recording the cueing signal. It is a cue signal recording circuit for removing noise generated from the oscillation circuit to the voice erasing head by a capacitor inserted between the voice erasing head and a secondary coil.

(E) Operation According to the cue signal recording circuit of the present invention, by inserting a capacitor between the secondary coil of the oscillator circuit and the voice erasing head, the voice erasing head is erased from the oscillator circuit when the cue signal is recorded. The nozzles that generate the electric current are removed.

(F) Embodiment The details of the present invention will be specifically described with reference to the illustrated embodiment.

FIG. 1 is a circuit diagram showing a cue signal recording circuit of the present invention. Describing the drawing number and the structure of FIG. 1, FIG. 1 has the same constituent elements as those of FIG. 2, that is, the same drawing number. In other than that, (27) is an oscillation circuit (26) The arbitrary point of the next coil (6) and the voice erasing head (1
0) is a capacitor inserted between the ends. The power supply voltage input to the power supply terminals (1) and (16) may be common.

The operation will be described below with reference to FIG. First, when the power supply voltage is input to the power supply terminal (1), the base potential of the transistor (2) repeatedly rises and falls through the coil (5) and the primary coil (3), and from this, the secondary coil (6)
Generates a voltage corresponding to the voltage on the primary coil (3) side.
When recording the audio signal input to the audio terminal (14), the amplifier (15) is added to the signal of the oscillation frequency of, for example, 70 KHz output through the capacitor (8) and the resistor (9).
The audio signal amplified by is superposed, and the superposed signal is AC bias recorded on the magnetic tape (25) by the audio head (7).

Next, when a cue signal is recorded on the magnetic tape (25), the power supply voltage is applied to the power supply terminal (16) via the resistor (18) and the transistor (23) is applied to the input terminal (22) via the resistor (24). )
A control signal for turning off is input. This control signal causes the base of the transistor (20) to be in a non-grounded state. The third input to the input terminal (19) through the resistor (21)
When the control signal shown in (b) rises, its base potential rises to turn on the transistor (20), and its base is grounded to turn off the transistor (17). On the other hand, when the control signal input to the input terminal (19) falls, its base potential drops to turn off the transistor (20), and its base potential rises to turn on the transistor (17). That is, the transistors (17) (20) are switched by the control signal input to the input terminal (19). Further, the impedance of the full width erasing head (11) is changed to either the collector-emitter of the transistor (17) or the coil (12) by the switching of the transistor (17), so that it is output from the oscillation circuit (26). The amplitude of the signal to be read is varied as shown in Fig. 3 (a).
It is recorded in 5).

Here, a counter electromotive force is generated in the secondary coil (6) in synchronization with the switching of the transistor (17), but the differential waveform shown in FIG. 4 (a) is removed by the capacitor (27),
As a result, the erasing current of the voice erasing head (10) becomes the same as that shown in Fig. 3 (a), and noise is generated even when the cue signal portion recorded on the magnetic tape (25) is reproduced by the voice head (7). It never happens. Further, the differential waveform generated by the back electromotive force of the secondary coil (6) is removed by the capacitor (8) and the resistor (9) and does not affect the recording current of the audio head (7).

(G) Effect of the Invention According to the cueing signal recording circuit of the invention, a simple structure in which a capacitor is inserted between the secondary coil of the oscillating circuit and the sound erasing head allows the sound to be output from the oscillating circuit when the cueing signal is recorded. It is possible to remove the noise generated in the erase current of the erase head.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a cue signal recording circuit of the present invention, FIG. 2 is a circuit diagram showing a conventional cue signal recording circuit, and FIG. 3 is a cue signal recording circuit in FIGS. 1 and 2. 2 is a timing chart showing the erase current envelope of the full-width erase head synchronized with the control signal for
7 is a timing chart showing an erasing current envelope of a voice erasing head synchronized with a control signal for recording a cue signal. Description of main drawing numbers (6) …… Secondary coil, (10) …… Voice erasing head,
(11) …… Full width erasing head, (17) (20) …… Transistor, (25) …… Magnetic tape, (26) …… Oscillation circuit,
(27) …… Capacitor.

Claims (1)

[Scope of utility model registration request] 1. A magnetic recording / reproducing apparatus for recording a cue signal on a magnetic tape with a full-width erasing head whose impedance is varied by a switching element to which a control signal for cue signal recording is input. At the time of recording a signal, a voice erasing head and the full width erasing head and its 2
Noise that is generated in the voice erasing head from the oscillation circuit for AC bias recording to which the secondary coil is connected is removed by a capacitor inserted between the voice erasing head and the secondary coil. circuit.