US5043676A
Expired / Lapsed
US
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Automatic level control circuit
Assignee: Pioneer Corp
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Filing: 1987-08-25
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Granted: 1991-08-27
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Expires: 2007-08-25
Abstract
Abstract In an ALC circuit for automatically performing an amplitude compression control operation according to the output level of a low frequency amplifier circuit, the output level of the amplifier circuit is subjected to amplitude compression according to the level of a control signal which is outputted in correspondence to the output level of the amplifier circuit. The differentiation time constant of a differentiating circuit (or cutoff frequency of a high pass filter) provided on the output side of the amplifier circuit is controlled according to the level of the control signal to control the cutoff frequency for the frequency band subjected to amplitude compression.
Inventors
- 👤 Takeshi Sato
- 👤 Hideo Yamamoto
- 👤 Toshikazu Yoshimi
- 👤 Shuichi Mori
- 👤 Akio Tokumo
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:24
CPC Classifications
H; H03; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3005; H03G3/301; H03G3/3015; H03G9/00; H03G9/02; H03G9/025
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
131 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio input signal having both low frequency and high frequency components within an audio frequency range, and for providing a level-controlled audio output signal, said ALC circuit comprising: control signal generating means for outputting a control signal corresponding to a level of said level-controlled audio output signal; and amplitude compression means for cutting off low frequency components of said level-controlled audio output signal below a predetermined frequency while passing said high frequency components from said audio input signal to said level-controlled audio output signal at all times without substantial attenuation, said predetermined frequency being varied by said control signal, and wherein said predetermined frequency is variable over a range which includes frequencies on the order of 315 Hz.
Claim 2
Dependent Claim
131 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio input signal having both low frequency and high frequency components within an audio frequency range, and for providing a level-controlled audio output signal, said ALC circuit comprising: control signal generating means for outputting a control signal corresponding to a level of said level-controlled audio output signal; and amplitude compression means for cutting off low frequency components of said level-controlled audio output signal below a predetermined frequency while passing said high frequency components from said audio input signal to said level-controlled audio output signal at all times without substantial attenuation, said predetermined frequency being varied by said control signal, and wherein said predetermined frequency is variable over a range which includes frequencies on the order of 315 Hz.
Claim 3
Dependent Claim
33 words
An ALC circuit as recited claim 1, wherein said amplitude compression means is a high pass filter with a variable cutoff frequency and said cut off frequency is controlled by said control signal.
Claim 4
Dependent Claim
31 words
An ALC circuit as recited in claim 2, wherein said high pass filter has a transfer function proportional to a frequency of said audio signal substantially less than said cutoff frequency.
Claim 5
Dependent Claim
31 words
An ALC circuit as recited in claim 2, wherein said high pass filter has a substantially flat transfer function in a frequency band with frequencies substantially less than said cutoff frequency.
Claim 6
Dependent Claim
17 words
An ALC circuit as recited in claim 1, wherein said amplitude compression means is a differentiating circuit.
Claim 7
Dependent Claim
47 words
An ALC circuit is recited in claim 5, wherein said differentiating circuit comprises: a capacitor receiving on a first terminal said audio signal; and two Darlington-connected transistors connected to a second terminal of said capacitor, said control signal being applied to a base of said Darlington-connected transistors.
Claim 8
Dependent Claim
35 words
An ALC circuit as recited in claim 6, wherein an input terminal to said control signal generating means and an output terminal of said ALC circuit are connected to said second terminal of said capacitor.
Claim 9
Dependent Claim
147 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components within an audio frequency range, comprising: control signal generating means for outputting a control signal corresponding to a level of said audio signal; and amplitude compression means for subjecting a variable frequency band of said low frequency component of said audio signal to amplitude compression while passing said high frequency component at all times without substantial attenuation, said frequency band being varied by said control signal over a range which includes frequencies on the order of 315 Hz, said amplitude compression means comprising a high pass filter with a variable cutoff frequency and said cutoff frequency is controlled by said control signal, said high pass filter having a transfer function proportional to a frequency of said audio signal substantially less than said cutoff frequency.
Claim 10
Dependent Claim
147 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components within an audio frequency range, comprising: control signal generating means for outputting a control signal corresponding to a level of said audio signal; and amplitude compression means for subjecting a variable frequency band of said low frequency component of said audio signal to amplitude compression while passing said high frequency component at all times without substantial attenuation, said frequency band being varied by said control signal over a range which includes frequencies on the order of 315 Hz, said amplitude compression means comprising a high pass filter with a variable cutoff frequency and said cutoff frequency is controlled by said control signal, said high pass filter having a transfer function proportional to a frequency of said audio signal substantially less than said cutoff frequency.
Claim 11
Dependent Claim
137 words
An automatic level control (ALC) circuit for receiving an input signal having both low frequency and high frequency components within an audio frequency range and automatically performing amplitude compression on said input signal to provide an output audio signal, said circuit comprising: a buffer amplifier for receiving said input signal; amplitude compression means coupled to the output of said buffer amplifier for subjecting a variable frequency band of said low frequency component of said input signal to amplitude compression while passing said high frequency components at all times without substantial attenuation to produce said output audio signal, said frequency band being varied by a control signal over a range which includes frequencies on the order of 315 Hz; and control signal generating means for outputting a control signal corresponding to a level of said output audio signal.
Claim 12
Dependent Claim
137 words
An automatic level control (ALC) circuit for receiving an input signal having both low frequency and high frequency components within an audio frequency range and automatically performing amplitude compression on said input signal to provide an output audio signal, said circuit comprising: a buffer amplifier for receiving said input signal; amplitude compression means coupled to the output of said buffer amplifier for subjecting a variable frequency band of said low frequency component of said input signal to amplitude compression while passing said high frequency components at all times without substantial attenuation to produce said output audio signal, said frequency band being varied by a control signal over a range which includes frequencies on the order of 315 Hz; and control signal generating means for outputting a control signal corresponding to a level of said output audio signal.
Claim 13
Dependent Claim
156 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components and representing sound, comprising: capacitance means (14) having an input terminal for receiving said audio signal as an input and an output terminal for providing an output audio signal to be reproduced as said sound; control signal generating means d.c. coupled to said output terminal of said capacitance means for providing a control signal corresponding to a level of said output audio signal; and variable resistance means responsive to said control signal for varying a d.c. resistance between said output terminal and a reference voltage to cut off said low frequency components of said audio signal below a predetermined frequency while passing said high frequency components at all times without substantial attenuation, said predetermined frequency being varied by said control signal over a range which includes frequencies on the order of 315 Hz.
Claim 14
Dependent Claim
156 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components and representing sound, comprising: capacitance means (14) having an input terminal for receiving said audio signal as an input and an output terminal for providing an output audio signal to be reproduced as said sound; control signal generating means d.c. coupled to said output terminal of said capacitance means for providing a control signal corresponding to a level of said output audio signal; and variable resistance means responsive to said control signal for varying a d.c. resistance between said output terminal and a reference voltage to cut off said low frequency components of said audio signal below a predetermined frequency while passing said high frequency components at all times without substantial attenuation, said predetermined frequency being varied by said control signal over a range which includes frequencies on the order of 315 Hz.
Claim 15
Dependent Claim
131 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio input signal having both low frequency and high frequency components within an audio frequency range, and for providing a level-controlled audio output signal, said ALC circuit comprising: control signal generating means for outputting a control signal corresponding to a level of said level-controlled audio output signal; and amplitude compression means for cutting off low frequency components of said level-controlled audio output signal below a predetermined frequency while passing said high frequency components from said audio input signal to said level-controlled audio output signal at all times without substantial attenuation, said predetermined frequency being varied by said control signal, and wherein said predetermined frequency is variable over a range which includes frequencies on the order of 50 Hz.
Claim 16
Dependent Claim
131 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio input signal having both low frequency and high frequency components within an audio frequency range, and for providing a level-controlled audio output signal, said ALC circuit comprising: control signal generating means for outputting a control signal corresponding to a level of said level-controlled audio output signal; and amplitude compression means for cutting off low frequency components of said level-controlled audio output signal below a predetermined frequency while passing said high frequency components from said audio input signal to said level-controlled audio output signal at all times without substantial attenuation, said predetermined frequency being varied by said control signal, and wherein said predetermined frequency is variable over a range which includes frequencies on the order of 50 Hz.
Claim 17
Dependent Claim
34 words
An ALC circuit as recited in claim 11, wherein said amplitude compression means is a high pass filter with a variable cutoff frequency and said cut off frequency is controlled by said control signal.
Claim 18
Dependent Claim
31 words
An ALC circuit as recited in claim 12, wherein said high pass filter has a transfer function proportional to a frequency of said audio signal substantially less than said cutoff frequency.
Claim 19
Dependent Claim
31 words
An ALC circuit as recited in claim 12, wherein said high pass filter has a substantially flat transfer function in a frequency band with frequencies substantially less than said cutoff frequency.
Claim 20
Dependent Claim
17 words
An ALC circuit as recited in claim 11, wherein said amplitude compression means is a differentiating circuit.
Claim 21
Dependent Claim
47 words
An ALC circuit as recited in claim 15, wherein said differentiating circuit comprises: a capacitor receiving on a first terminal said audio signal; and two Darlington-connected transistors connected to a second terminal of said capacitor, said control signal being applied to a base of said Darlington-connected transistors.
Claim 22
Dependent Claim
35 words
An ALC circuit as recited in claim 16, wherein an input terminal to said control signal generating means and an output terminal of said ALC circuit are connected to said second terminal of said capacitor.
Claim 23
Dependent Claim
147 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components within an audio frequency range, comprising: control signal generating means for outputting a control signal corresponding to a level of said audio signal; and amplitude compression means for subjecting a variable frequency band of said low frequency component of said audio signal to amplitude compression while passing said high frequency component at all times without substantial attenuation, said frequency band being varied by said control signal over a range which includes frequencies on the order of 50 Hz, said amplitude compression means comprising a high pass filter with a variable cutoff frequency and said cutoff frequency is controlled by said control signal, said high pass filter having a transfer function proportional to a frequency of said audio signal substantially less than said cutoff frequency.
Claim 24
Dependent Claim
147 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components within an audio frequency range, comprising: control signal generating means for outputting a control signal corresponding to a level of said audio signal; and amplitude compression means for subjecting a variable frequency band of said low frequency component of said audio signal to amplitude compression while passing said high frequency component at all times without substantial attenuation, said frequency band being varied by said control signal over a range which includes frequencies on the order of 50 Hz, said amplitude compression means comprising a high pass filter with a variable cutoff frequency and said cutoff frequency is controlled by said control signal, said high pass filter having a transfer function proportional to a frequency of said audio signal substantially less than said cutoff frequency.
Claim 25
Dependent Claim
137 words
An automatic level control (ALC) circuit for receiving an input signal having both low frequency and high frequency components within an audio frequency range and automatically performing amplitude compression on said input signal to provide an output audio signal, said circuit comprising: a buffer amplifier for receiving said input signal; amplitude compression means coupled to the output of said buffer amplifier for subjecting a variable frequency band of said low frequency component of said input signal to amplitude compression while passing said high frequency components at all times without substantial attenuation to produce said output audio signal, said frequency band being varied by a control signal over a range which includes frequencies on the order of 50 Hz; and control signal generating means for outputting a control signal corresponding to a level of said output audio signal.
Claim 26
Dependent Claim
137 words
An automatic level control (ALC) circuit for receiving an input signal having both low frequency and high frequency components within an audio frequency range and automatically performing amplitude compression on said input signal to provide an output audio signal, said circuit comprising: a buffer amplifier for receiving said input signal; amplitude compression means coupled to the output of said buffer amplifier for subjecting a variable frequency band of said low frequency component of said input signal to amplitude compression while passing said high frequency components at all times without substantial attenuation to produce said output audio signal, said frequency band being varied by a control signal over a range which includes frequencies on the order of 50 Hz; and control signal generating means for outputting a control signal corresponding to a level of said output audio signal.
Claim 27
Dependent Claim
156 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components and representing sound, comprising: capacitance means (14) having an input terminal for receiving said audio signal as an input and an output terminal for providing an output audio signal to be reproduced as said sound; control signal generating means d.c. coupled to said output terminal of said capacitance means for providing a control signal corresponding to a level of said output audio signal; and variable resistance means responsive to said control signal for varying a d.c. resistance between said output terminal and a reference voltage to cut off said low frequency components of said audio signal below a predetermined frequency while passing said high frequency components at all times without substantial attenuation, said predetermined frequency being varied by said control signal over a range which includes frequencies on the order of 50 Hz.
Claim 28
Dependent Claim
156 words
An automatic level control (ALC) circuit for automatically performing amplitude compression on an audio signal having both low frequency and high frequency components and representing sound, comprising: capacitance means (14) having an input terminal for receiving said audio signal as an input and an output terminal for providing an output audio signal to be reproduced as said sound; control signal generating means d.c. coupled to said output terminal of said capacitance means for providing a control signal corresponding to a level of said output audio signal; and variable resistance means responsive to said control signal for varying a d.c. resistance between said output terminal and a reference voltage to cut off said low frequency components of said audio signal below a predetermined frequency while passing said high frequency components at all times without substantial attenuation, said predetermined frequency being varied by said control signal over a range which includes frequencies on the order of 50 Hz.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-08-26 | 1995-02-25 | 1995-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-26 | 1999-02-25 | 1999-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-26 | 2003-02-25 | 2003-08-27 | $7700.00 | Window Closed / Lapsed |