JPS5850501Y2 - magnetic recording and playback device - Google Patents

Description

[Detailed description of the invention] The present invention enables easy and cost-effective detection of the start and end of a video signal on a recorded tape in a magnetic recording/playback device by digitally processing the presence or absence of a playback control signal or a signal synchronized therewith. The aim is to reduce the

A block diagram of one embodiment of the present invention is shown in FIG. 1, and a timing chart thereof is shown in FIG. 2.The following describes the case in which the playback control signal and one monostable multivibrator of the present invention are used with reference to the figures.

During playback of a recorded tape, a playback control signal is played back from the playback control head, and is amplified by the playback control amplifier 1 shown in Fig. 1 to obtain the Fig. 2-81 signal. Input to break 2.

The amount of delay of this monostable multivibrator 2 is determined by resistor R1 and capacitor C0, and if this amount of delay is set to at least the period (33.3 ms) of the reproduction control signal, the period during which the reproduction control signal exists The medium monostable multivibrator output continues to maintain a high level.

Next, when the video signal disappears (as shown by the dotted line in Figure 2 81), the output of the monostable multivibrator 2 is changed from the last playback control signal to the monostable multivibrator
It becomes a low level after a delay amount T1.

The output signal S2 of this monostable multivibrator 2 is input to a differentiating circuit (including a rectifier circuit, etc.) 3, and when the output signal s2 of the monostable multivibrator 2 falls, a pulse signal S2 is generated.
3 is obtained, and this is used as the end detection signal of the video signal of the recorded tape.

Detecting the end of a recorded tape during fast forwarding in the same way as above,
Starting edge detection during rewinding is also possible.

A block diagram of another embodiment of the present invention is shown in FIG. 3, and a timing chart thereof is shown in FIG. 4.

This is the case using a playback control signal and two monostable multivibrators.

During playback of a recorded tape, a playback control signal is played back from the playback control head and amplified by the playback control amplifier 4 shown in FIG. 3 to obtain the signal 81 in FIG. 4, which is used to trigger two playback triggers. Input into possible monostable multi-by-breaks 5 and 6, respectively.

The delay amount of the monostable multi-bi break 5 is determined by the resistor R2 and the capacitor C2, and the delay amount of the monostable multi-bi break 6 is determined by the resistor R3 and the capacitor C3.
33.3 ms) or more, and the delay amount of the monostable multivibrator 5 is set to be longer than the delay amount of the monostable multivibrator 6.

As a result, the two monostable multi-bi break outputs continue to maintain a high level while the playback control signal is present.

Next, when there is no video signal, that is, there is no playback control signal (as shown by the dotted line in Figure 4, 81).
has two monostable multi-by-breaks 5 and 6 output S4.
．． S, becomes low level after respective delay amounts T2 and T3 from the last reproduction control signal.

The output signal S4 of this monostable multivibrator 5, the output signal S of the monostable multivibrator, and the opposite output signal S
, and are input to the AND gate circuit 7, an AND gate output signal S6 having a pulse width equal to the difference T2-T3 between the delay amounts of the two monostable multi-bi breaks 5 and 6 is obtained.

This signal S6 is then used as an end detection signal of the video signal of the recorded tape.

Detecting the end of a recorded tape during fast forwarding in the same way as above,
Starting edge detection during rewinding is also possible.

In the present invention, instead of the reproduction control signal during reproduction, a signal synchronized with this signal or a vertical synchronization signal synchronously separated from the reproduced video signal may be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a timing chart of the same embodiment, FIG. 3 is a block diagram of another embodiment, and FIG. 4 is a timing chart of the same embodiment. 1.4...Reproduction control signal amplifier, 2゜5.6...Retrigger monostable multi-vibration break, 3...Differentiating circuit, 7...・And gate.

Claims (2)

[Scope of utility model registration request] (1) A playback control signal (including fast forwarding and rewinding) or a signal synchronized therewith is input to a retriggerable monostable multi-by-break, and the delay time of the monostable multi-by-break is at least equal to the play control signal or this signal. The output of the monostable multivibrator is set to a period greater than or equal to the period of the signal synchronized with the playback control signal or the signal synchronized therewith, and the output of the monostable multivibrator is used to detect the start and end of the video signal of the recorded tape. magnetic recording and playback device. (2) The magnetic recording and reproducing apparatus according to claim 1, wherein a vertical synchronizing signal synchronously separated from a reproduced video signal is used as an input to the retriggerable monostable multivibrator.