JPS5932046Y2 - Record start search mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording start end search mechanism that makes it possible to search for a record start end.

At present, the cassette tape of a cassette type video tape recorder is capable of recording for 1 to 2 hours, and it is difficult to locate the beginning of recording in the middle of recording on the tape.

Therefore, the present invention proposes a recording start end search mechanism configured to record a control signal in one-sided polarity for a certain period of time at the start of recording, and to detect one-sided recorded portion of a control track in fast forward or rewind mode.

The present invention will be described below with reference to an illustrative embodiment.

FIG. 1 shows a circuit block diagram for implementing the present invention, and FIG. 2 is a waveform explanatory diagram of the same.

Figure 1 in Figure 1 is a vertical synchronization separation circuit that inputs the recorded video signal during recording and derives the vertical synchronization pulse A, 2 is a 1/frequency division circuit that divides the vertical synchronization pulse A, and 3 is a 2 a timer circuit that determines the unipolar recording period immediately after the start of recording;
4 is a unipolar Harsuwo for a certain period of time by the timer output C,
After that, the control signal recording circuit 5 applies a bipolar pulse to the control head HD, and 6 is a first amplifier that amplifies the playback control output E. 6 is a second amplifier that re-amplifies the first amplifier output during playback. γ is a second amplifier. A tracking adjustment circuit that delays the amplifier output for tracking adjustment, 8 a positive polarity amplifier that amplifies and derives only the positive pulse F in the output of the first amplifier, and 9 amplifies and derives only the negative pulse G in the output of the first amplifier. A negative polarity amplifier 10 derives a positive polarity pulse F as a clock pulse ■ and a negative polarity pulse G as a reset pulse H during fast forward reproduction, and derives a negative polarity pulse F as a clock pulse ■ during rewind reproduction, and outputs a positive polarity pulse F as a clock pulse ■. Switching circuit for deriving reset pulse F as reset pulse H, 1
Reference numeral 1 represents a 2-bit counter which inputs the clock pulse (2) and the reset pulse H to detect the omission of the reset pulse, that is, the arrival of a unipolar recording section.

Therefore, according to this embodiment, when a recording operation is started without switching, the output B of the /2 frequency divider circuit 2 is applied to the servo circuit as a rotation reference signal of the capstan motor and/or the rotary rotor motor. The control signal is applied to the recording circuit 4.

When the timer circuit output C is applied to the control signal recording circuit 4 in such a state, a positive polarity pulse is derived from the control signal recording circuit 4 for a certain period of time, and unipolar recording is performed on the control track. A polar pulse and a negative pulse are alternately derived to perform bipolar recording.

Therefore, when normally playing back such a recording tape, if the positive polarity pulse during recording is applied to the servo circuit as a running detection output to control the rotation of the capstan motor, the presence of the unipolar recording section will not interfere with playback. It is not.

Next, the cueing operation will be explained.

When searching for the recording start end while the tape is in fast forward mode, the positive pulse F of the playback controller is input as the clock pulse ■, and the negative pulse G is input as the reset pulse H to the counter circuit 11. .

Therefore, when the unipolar recording section of the tape running with fast-forward playback passes the control head H, the reset pulse H is missing, so the counter circuit 11 counts a number of 2 or more and outputs the upper bit J. is derived as a stop signal, the automatic stop plunger is energized, and the tape is stopped at the recording start end, that is, at the unipolar recording section.

Additionally, when rewinding the tape (at high speed) and searching for the recording start end, the polarity of the playback control signal is reversed, so the negative polarity pulse G is used as the clock pulse ■, and the positive polarity pulse G is used as the reset pulse H. By inputting the signal to the counter circuit 11, the tape can be stopped in the same manner as described above.

Hereinafter, specific circuit operations of the timer circuit 3 and the control signal recording circuit 4 will be briefly explained with reference to the circuit diagram of FIG. 3 and the waveform explanatory diagram of FIG. 4.

In FIG. 3, the control signal recording circuit 4 includes a bootstrap circuit for unipolar recording consisting of a first transistor Q1 and a charging/discharging capacitor C1, and a gate consisting of second to fifth transistors Q2 to Q5. The circuit includes a second capacitor C2 that forms a differential circuit together with the head winding coil, and includes sixth and seventh transistors Q6. Q7
The opening/closing of the gate is controlled by the output of a timer circuit composed of a delay capacitor C3 and a positive polarity pulse related to the footstrap output for a certain period (for example, about 0.4 seconds) immediately after the start of recording, and then 1/ It operates to derive bipolar pulses related to the divide-by-2 output.

More specifically, the 1/2 frequency-divided output is connected to the 6th gate of the fourth transistor Q4 constituting the second manual stage of the gate circuit;
The bootstrap output C, which has a gentle fall and is input to the base of the first PNP transistor Q□ constituting the bootstrap input stage and is delivered to the collector of the first transistor Q1, is connected to the second human input stage of the gate circuit. It is applied to the base of the third transistor Q3.

When the power is turned on in conjunction with the recording mode setting, the delay capacitor C3 is charged and turns on the sixth transistor Q6 after 0.4 seconds, and turns off the seventh transistor Q7 which is in the on state at the same time as the power is turned on. shall be.

Therefore, the collector output e of the seventh transistor is connected to the base of the second transistor Q2 whose collector-emitter is connected between the base and ground of the third transistor Q3, and the emitter-collector is connected between the base and ground of the fourth transistor Q4. The base of the fifth transistor Q5 is connected to the sixth transistor Q5.
When the collector output d of the transistor is input, the first manual stage of the gate circuit is opened for 0.4 seconds immediately after the start of recording.
Thereafter, the second power stage is opened, and the third and fourth transistors Q3. A gate output f is derived from the common emitter of Q4, and a differential output of the gate output f is applied to the control head HD.

Therefore, in this embodiment, approximately 12
Although unipolar recording is performed over the frame, the unipolar recording period must be increased or decreased as necessary.

As described above, according to the present invention, the control track at the beginning of recording is recorded in a unipolar manner, and the unipolar recording section of the control track is searched in the fast forward and rewind states to automatically stop the tape, so that recording during playback is not possible. At the beginning, the capstan servo circuit is not disturbed and the effect is excellent.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an implementation circuit of the present invention, FIG. 2 is an explanatory diagram of the same waveforms, FIG. 3 is a circuit diagram of the main part thereof, and FIG. 4 is an explanatory diagram of the same waveforms. Explanation of main drawing numbers, 3...Timer, 4...Control signal recording circuit, HD...Control head, 8
...Positive polarity amplifier, 9...Negative polarity amplifier, J...
Stop signal.

Claims (1)

[Scope of utility model registration request] In a video tape recorder that forms a control track in the longitudinal direction of a magnetic tape, there is a timer circuit that issues a delayed output with respect to the recording start timing, a unipolar control pulse immediately after recording starts, and a bipolar pulse that controls a bipolar pulse after the delayed output occurs. A recording start end comprising: a control signal recording circuit that applies a control signal to the head; and a recording start detection circuit that separates the polarity of the playback control signal in fast-forward and rewind states, detects a unipolar recording section, and generates a stop signal. Search mechanism.