# US 4,396,955 A · Muting device

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- Number: US 4,396,955 A
- Document ID: US4396955A
- Status: Granted
- Kind: A
- Application number: 06/275,360
- Filed: 1981-06-19
- Granted: 1983-08-02
- Earliest claimed: 1980-06-25
- Assignees: Canon Kabushiki Kaisha
- Inventors: Yutaka Kohtani; Tadao Udagawa
- Web page: https://patentgrep.com/patent/US4396955A

## CPC

- H03G 3/348: {Muting in response to a mechanical action or to power supply variations, e.g. during tuning; Click removal circuits}
- G11B 5/02: Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
- G11B 20/02: Analogue recording or reproducing
- H03G: CONTROL OF AMPLIFICATION
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

In a recording apparatus for performing magnetic recording onto different parts of a magnetic recording medium as it runs in sequence, a switching element is connected in series in a signal path to a magnetic head which is connected to the output of the signal amplifier and to a bias oscillator. Accordingly, the signal current flowing to the magnetic head can be interrupted. A delay circuit is provided for controlling the operation of the switching element so as to defer initiation of the signal current flow to the magnetic head. This is done pending attainment of the speed of movement of the magnetic recording medium to a substantially constant level after the magnetic recording starts. Connected in parallel to the switching element is a by-pass circuit of which the impedance is relatively low at a frequency equal to that of the bias supplied to the magnetic head. A stabilized muting effect from the low to the high sound region thus can be produced.

## Claims

### Claim 1

A muting device for use in magnetic recording apparatus in which magnetic recordings are produced by a magnetic head onto different portions of a relatively movable magnetic recording medium when signal currents flow through a signal path including said magnetic head, comprising:
(a) switching means connected in the signal path of the magnetic head in series to said magnetic head so that a signal current flowing to said magnetic head can be interrupted;
(b) release means for producing a release signal for initiating relative movement of the magnetic recording medium with respect to said magnetic head; and
(c) delay control means for rendering the switching means conductive after the elapse of a predetermined time from the production of said release signal from said release means, and including bias means for biasing said signal current flowing to the magnetic head by a high frequency wave, and by-pass means connected in parallel to said switching means wherein the impedance of said by-pass means is lowered at the frequency of said high frequency bias.

### Claim 2 (depends on 1)

A muting device according to claim 1, wherein said by-pass means comprises a series resonant circuit which is resonant at the frequency of the high frequency bias.

### Claim 3 (depends on 1)

A muting device according to claim 1, wherein said by-pass means comprises a condenser having a low impedance value for the frequency of the high frequency bias and a high impedance value at sound signal frequencies.

### Claim 4

A muting device for use in magnetic recording apparatus in which magnetic recordings are produced by a magnetic head onto different portions of a relatively movable magnetic recording medium when signal currents flow through a signal path including said magnetic head, comprising:
(a) switching means connected in the signal path of the magnetic head in series to said magnetic head so that a signal current flowing to said magnetic head can be interrupted;
(b) release means for producing a release signal for initiating relative movement of the magnetic recording medium with respect to said magnetic head; and
(c) delay control means for rendering the switching means conductive after the elapse of a predetermined time from the production of said release signal from said release means, and including a high frequency oscillator having an output for biasing said signal current flowing to the magnetic head, and the high frequency oscillator and said switching means are arranged to cooperate with each other so that during the time when the switching means interrupts the signal current flowing to the magnetic head, the high frequency oscillator ceases oscillation, and during the time when said signal current is allowed to flow to the magnetic head, the high frequency oscillator oscillates.