GB941704A - Improvements in or relating to electric circuit arrangements for transmitting electrical signals representative of sound signals - Google Patents

Improvements in or relating to electric circuit arrangements for transmitting electrical signals representative of sound signals

Info

Publication number
GB941704A
GB941704A GB583259A GB583259A GB941704A GB 941704 A GB941704 A GB 941704A GB 583259 A GB583259 A GB 583259A GB 583259 A GB583259 A GB 583259A GB 941704 A GB941704 A GB 941704A
Authority
GB
United Kingdom
Prior art keywords
gate
pulse
capacitor
pulses
control
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB583259A
Inventor
Michael Batchelor
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EMI Ltd
Electrical and Musical Industries Ltd
Original Assignee
EMI Ltd
Electrical and Musical Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EMI Ltd, Electrical and Musical Industries Ltd filed Critical EMI Ltd
Priority to GB583259A priority Critical patent/GB941704A/en
Publication of GB941704A publication Critical patent/GB941704A/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03KPULSE TECHNIQUE
    • H03K7/00Modulating pulses with a continuously-variable modulating signal
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03GCONTROL OF AMPLIFICATION
    • H03G3/00Gain control in amplifiers or frequency changers
    • H03G3/20Automatic control
    • H03G3/22Automatic control in amplifiers having discharge tubes
    • H03G3/26Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise, e.g. squelch systems
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03GCONTROL OF AMPLIFICATION
    • H03G5/00Tone control or bandwidth control in amplifiers
    • H03G5/16Automatic control
    • H03G5/165Equalizers; Volume or gain control in limited frequency bands

Landscapes

  • Electrophonic Musical Instruments (AREA)

Abstract

941,704. Automatic volume control. ELECTRIC & MUSICAL INDUSTRIES Ltd. Feb. 22, 1960 [Feb. 20, 1959], No. 5832/59. Headings H4J and H4R. In a circuit for reducing impulsive interference, such as that derived from unwanted displacements of a gramophone stylus, a blocking pulse whose duration is dependent upon the duration of the interference is applied to a gate arranged so that at least high frequency components of electrical signals applied to the circuit are attenuated during the application of the blocking pulse. A signal from an input 1, Fig. 1, is separated into low and high frequency components by a low-pass filter 2 in channel 3 and a high-pass filter 4 in a channel 5. Channel 5 also includes a gate 6 which is normally open but is closed by blocking pulses from a channel 7. The channel 7 includes a threshold control 8, in the form of a potentiometer, and an interfering pulse identification unit 9. A delay line 10 ensures that the gate 6 is closed before an interfering pulse arrives at the gate. Outputs from channels 3, 5 are combined and applied to an output gain control 11. The common cut-off frequency of filters 2 and 4 may be adjustable to 1,000 or 500 c/s. The low-pass filter may be omitted and the high-pass filter by-passed. The threshold control 8 and interfering pulse identification unit 9 includes a pentode amplifier V1, Fig. 2, to which a portion of the signal is applied, and a high-pass filter F which transmits frequencies above 16 kc/s to a variable potentiometer VR1 acting as the threshold control and controlling the level of the signal applied to an amplifier V2a. The output of amplifier V2a is fed to a monostable multivibrator V3 which generates a square wave output whenever the voltage of the signal applied thereto exceeds the triggering voltage. The square wave output is fed through a cathode follower V2b and rectifier V5a to a monostable multivibrator V4. This derives by means of capacitor C1 output pulses X and Y having a duration equal to that of the triggering signals plus about one millisecond. The pulses X are negative and are applied through a cathode follower V8a, Fig. 3, to a gate V7 in the form of a double triode acting as a push-pull class A amplifier. They are fed to the centre tap of an input transformer T1 so as to bias the control electrodes of amplifier V7 well beyond cut-off, a diode V9a being employed to clamp the quiescent control electrode potential. Controls VR3 and VR4 equalize the two sections of gate V7 and are adjusted for minimum hum after injecting a 50 c/s. signal at switch S1 (see Fig. 2). A by-pass capacitor C3 reduces the slope of the leading edge of the pulse X, and also to a certain extent its trailing edge, to cause the gate V7 to close and open slowly, in approximately ¢ millisecond. Positive pulses 7 from multivibrator V4 are applied to terminal 13 and after rectification by rectifier V9b are fed to the control electrode of triode V8b. Whenever a pulse Y exists a needle of metre M is deflected. Discriminator.-The output from the threshold control VR1, Fig. 2, is also applied by a control VR2 to an amplifying stage V6 and then by a rectifier V5b to a capacitor C2. The capacitor charges slowly and the voltage across it is applied to the suppressor electrode of pentode V1 to reduce the gain of this stage. A single interfering pulse or short train of pulses will not reduce the gain of pentode V1 significantly but signals due to the programme and lasting more than a few milliseconds reduce the gain to cause the multivibrator V3 to cease. Thus the duration of a short pulse or short train of pulses will determine the length of time the gate is closed. A continuous signal of more than a few milliseconds duration which charges capacitor C2 will cause the gate to open after the capacitor C2 has charged.
GB583259A 1959-02-20 1959-02-20 Improvements in or relating to electric circuit arrangements for transmitting electrical signals representative of sound signals Expired GB941704A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB583259A GB941704A (en) 1959-02-20 1959-02-20 Improvements in or relating to electric circuit arrangements for transmitting electrical signals representative of sound signals

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB583259A GB941704A (en) 1959-02-20 1959-02-20 Improvements in or relating to electric circuit arrangements for transmitting electrical signals representative of sound signals

Publications (1)

Publication Number Publication Date
GB941704A true GB941704A (en) 1963-11-13

Family

ID=9803465

Family Applications (1)

Application Number Title Priority Date Filing Date
GB583259A Expired GB941704A (en) 1959-02-20 1959-02-20 Improvements in or relating to electric circuit arrangements for transmitting electrical signals representative of sound signals

Country Status (1)

Country Link
GB (1) GB941704A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4076969A (en) * 1975-04-07 1978-02-28 Singer & Singer Impulse noise reduction system
US4119812A (en) * 1977-04-20 1978-10-10 Rca Corporation Signal defect detection and compensation with signal de-emphasis
DE2854401A1 (en) * 1978-12-16 1980-06-19 Deutsche Fernsprecher Gmbh Long life telephone answering machine - has solid state memory with converters for changing between analog and digital operating modes
FR2489635A1 (en) * 1980-09-03 1982-03-05 Hitachi Ltd AUDIO SIGNAL NEUTRALIZATION CIRCUIT FOR MAGNETIC RECORDING AND REPRODUCING APPARATUS

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4076969A (en) * 1975-04-07 1978-02-28 Singer & Singer Impulse noise reduction system
US4119812A (en) * 1977-04-20 1978-10-10 Rca Corporation Signal defect detection and compensation with signal de-emphasis
DE2854401A1 (en) * 1978-12-16 1980-06-19 Deutsche Fernsprecher Gmbh Long life telephone answering machine - has solid state memory with converters for changing between analog and digital operating modes
FR2489635A1 (en) * 1980-09-03 1982-03-05 Hitachi Ltd AUDIO SIGNAL NEUTRALIZATION CIRCUIT FOR MAGNETIC RECORDING AND REPRODUCING APPARATUS

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