SU1597910A1 - Device for automatic search for required record portion on magnetic carrier - Google Patents

Abstract

The invention relates to a magnetic recording technique, in particular, to devices for searching portions of a recording in a cassette apparatus of magnetic recording, and allows increasing the reliability of detecting pauses between phonograms and reducing the requirements for the mechanical components of the device. The device further comprises a cascade 5 of switching parameters of the detector, a sensor 9 of the number of revolutions of the receiving or feeding coils of the tape cassette and a reversible controllable delay circuit. The detector with a controlled delay circuit operates on a signal directly related to the speed of the tape, namely the rotational frequency signal of the receiving or feeding coils of the tape cassette. 1 il.

Description

The invention relates to techniques for magnetic recording, and in particular to devices for searching recording sections in cassette equipment magnetic recording.

The purpose of the invention is to increase the reliability of detecting pauses between phonograms and reducing the requirements for the mechanical components of the device.

The drawing shows a functional diagram of the device.

A device for automatically searching for a desired recording area on a magnetic medium comprises a drive 1 connected to a control unit 2, a reproducing head 3 connected to a detector 4, to which an adjustment terminal of the detector parameter switching stage 5 is connected, the first input of which is connected to the output of the controlled delay circuit 6 and the second with an additional input of the control signal generating unit 7. The output of the controlled delay circuit 6 is connected to the control signal generating unit 7, the input of which receives signals from the number setting unit 8. The speed sensor 9 is connected to a controlled delay circuit 6.

The device operates as follows.

The initial state of the detector 4 and the reversed circuit 6 controlled delay corresponds to the absence of recording on magnetic tape. When the search is turned on, the control signal generating unit 7 according to the code coming from the number setting unit 8 gives a signal for switching on the forward or rewind mode. The control unit 2 generates an appropriate command and puts the drive 1 in the search mode in the desired direction. The tape moves and the reproducing head 3 removes the signal recorded on the tape, which is fed to the detector 4.

The detector switching cascade 5 provides four gradations of sensitivity and two gradations of the time constants of detector 4, which are set as follows.

In playback mode, the time constant of detector 4 is maximum, significantly greater than the maximum period of the signal recorded on the tape, but significantly shorter than the minimum pause between recording sections on magnetic tape (this condition must also be satisfied when the tape is rewound at maximum speed, in this mode, the time constant of the detector should be much less than in playback mode, i.e. minimal).

In the rewind mode, but the signal from the output of the control unit sets the sensitivity of the detector 4 lower than in the playback mode, in accordance with the ratio of the values of the signals recorded from the playback head 3 in these modes.

The output of the reversed circuit 6 controlled delay receives a signal about the absence of recording on magnetic tape, through which the sensitivity of the detector 4 is roughened by a certain amount both in playback mode and in rewind mode, which serves to eliminate the reverse switching of the search device due to possible interference with switching drive 1 from one mode to another.

The detector 4 converts the alternating voltage from the reproducing head 3 into a pulse signal about the presence of the recording area on the magnetic tape.

Since the time constant of the detector 4 is chosen small compared with the duration of the true pause between the recording sections on the magnetic tape, false pulses are possible in the signal from the detector. Exact selection by the duration of these pulses is carried out by a reversed controlled delay circuit 6, which measures the state of the output if, after changing the signal level at the information input, this level remains for a certain number of signal periods at the clock input of the controlled delay circuit 6. If the change in the input signal was short-term, then the output state does not change and after the end of such a search signal, the reversed circuit of the controlled delay is restored at a speed similar to that determined by the duration of the signal period at the clock input. This provides an integral estimate of the ratio of the duration of pauses and recording sections on magnetic tape.

The period of the signal from the sensor 9 of the number of revolutions of the receiving or feeding reel of the tape cassette is rigidly connected with the speed of the tape, therefore, the reversed controlled delay circuit successfully works with significant changes in the speed of the tape and the error in this unit occurs only due to a change in the diameter of the reel with the tape.

When a true pause is detected between the recording sections on the magnetic tape, the reversed circuit of the controlled delay by the output signal arriving at the detector switching parameter cascade 5 coarsens the detector parameters. The same signal is fed to the input of the control signal generating unit 7, which, upon receipt of the set number of the signal number of the number of signals of the reversed circuit of the controlled delay 6, set by the code of the unit 8, outputs a signal to the playback mode to the input of the control unit 2. The control unit 2 generates a command that puts the drive 1 in playback mode, and the signal from the auxiliary output to the cascade 5 of switching the detector parameters sets the sensitivity and time constant of the detector 4 optimal for this mode. Further, the operation of the device is repeated until the entire program.

Claims (1)

Claim A device for automatically searching for the desired recording area on a magnetic medium, containing a series-connected number setting unit, a control signal generating unit, a control unit and a drive, as well as a reproducing head connected to the detector, characterized in that, in order to increase the reliability of detecting pauses between phonograms and reducing requirements for the mechanical components of the device, it introduced a cascade of switching detector parameters, a sensor for the number of revolutions of the receiving or feeding coil of the cassette with a reverse and a controlled delay circuit, 5 the control output of the detector parameter switching stage is connected to a detector, the output of which is connected to the information input of the controlled delay circuit, and its output is connected to the input of the control signal generating unit and to the first control input of the detector parameter switching stage, the second control input of which is connected to an additional output of the control signal generating unit, and the output of the sensor 15 is the number of revolutions of the receiving or feeding coil networks with a tape connected to the clock input of a controlled delay circuit.