Compressing andor expanding circuit having non linear control circuitto reduce modulation noise

Claim 2

A compressing circuit comprising compressor means for compressing an input signal in response to a control signal applied thereto, signal level adjusting means for imparting a small attenuation amount to a signal supplied thereto when the level of said supplied signal is low and for imparting a large attenuation amOunt to said supplied signal when the level of said supplied signal is high, said signal level adjusting means being coupled to receive an output signal from said compressor means as said supplied signal, and control circuit means for generating said control signal in response to the level of a signal from said signal level adjusting means.

Claim 3

The compressing circuit according to claim 1, in which said compressor means includes a control element the resistance of which varies in response to said control signal, and said compressor means compresses the input signal supplied thereto in response to variations in resistance of said control element.

Claim 4

The compressing circuit according to claim 1, in which said signal level adjusting means adjusts the level of said supplied signal in a manner which enlarges the range of level variations of said input signal corresponding to the range of variations of said control signal.

Claim 5

The compressing circuit according to claim 1, in which said signal level adjusting means comprises at least one amplifier having a load circuit including a non-linear circuit element and a linear circuit element connected in series.

Claim 6

The compressing circuit according to claim 4, in which said linear circuit element is a resistor and said non-linear circuit element is a parallel combination of a pair of diodes connected in opposite polarity.

Claim 7

The compressing circuit according to claim 5, in which said resistor is a variable resistor.

Claim 8

An expanding circuit comprising expandor means for expanding an input signal in response to a control signal applied thereto, signal level adjusting means for imparting a small attenuation amount to a signal supplied thereto when the level of said supplied signal is low and for imparting a large attenuation amount to said supplied signal when the level of said supplied signal is high, said signal level adjusting means being coupled to receive an input signal from a compressing circuit means, and control circuit means for generating said control signal in response to the level of a signal from said signal level adjusting means.

Claim 9

An expanding circuit comprising expandor means for expanding an input signal in response to a control signal applied thereto, signal level adjusting means for imparting a small attenuation amount to a signal supplied thereto when the level of said supplied signal is low and for imparting a large attenuation amount to said supplied signal when the level of said supplied signal is high, said signal level adjusting means being coupled to receive an input signal from a compressing circuit means, and control circuit means for generating said control signal in response to the level of a signal from said signal level adjusting means.

Claim 10

The expanding circuit according to claim 7, in which said signal level adjusting means adjusts the level of said supplied signal in such a manner which enlarges the range of level variations of said input signal corresponding to the range of variations of said control signal.

Claim 11

The expanding circuit according to claim 7, in which said expandor means includes a control element the resistance of which varies in response to said control signal, and said expandor means expands the input signal supplied thereto in response to variations in resistance of said control element.

Claim 12

The expanding circuit according to claim 9, in which said expandor means comprises a negative feedback amplifier and said control element is connected to the negative feedback loop of said negative feedback amplifier.

Claim 13

The expanding circuit according to claim 7, in which said signal level adjusting means comprises at least one amplifier having a load circuit including a non-linear circuit element and a linear circuit element connected in series.

Claim 14

The expanding circuit according to claim 11, in which said linear circuit element is a resistor and said non-linear circuit element is a parallel combination of a pair of diodes connected in opposite polarity.

Claim 15

The expanding circuit according to claim 12, in which said resistor is a variable resistor.

Claim 16

A compandor circuit comprising a compressing circuit means comprising compressor means for compressing an input signal in response to a first control signal applied thereto, first signal level adjusting means for imparting a small attenuation amount to a signal supplied thereto when the level of said supplied signal is low and for imparting a large attenuation amount to said supplied signal when the level of said supplied signal is high, said first signal level adjusting means being coupled to receive an output signal from said comPressor means as said supplied signal, first control circuit means for generating said first control signal in response to the level of a signal from said first signal level adjusting means; transmission system means for transmitting the compressed signal from the compressing circuit to an expanding circuit means; said expanding circuit means comprising expandor means responsive to a second control signal for expanding an input signal applied thereto from said transmission system, second signal level adjusting means for imparting a small attenuation amount to a signal supplied thereto when the level of said signal supplied thereto is low and imparting a large attenuation amount to said signal supplied thereto when the level of said signal supplied thereto is high, said second signal level adjusting means being coupled to receive an input signal from said transmission system means, and second control circuit means for generating said second control signal in response to the level of signal from said second signal level adjusting means.

Claim 17

A compandor circuit comprising a compressing circuit means comprising compressor means for compressing an input signal in response to a first control signal applied thereto, first signal level adjusting means for imparting a small attenuation amount to a signal supplied thereto when the level of said supplied signal is low and for imparting a large attenuation amount to said supplied signal when the level of said supplied signal is high, said first signal level adjusting means being coupled to receive an output signal from said comPressor means as said supplied signal, first control circuit means for generating said first control signal in response to the level of a signal from said first signal level adjusting means; transmission system means for transmitting the compressed signal from the compressing circuit to an expanding circuit means; said expanding circuit means comprising expandor means responsive to a second control signal for expanding an input signal applied thereto from said transmission system, second signal level adjusting means for imparting a small attenuation amount to a signal supplied thereto when the level of said signal supplied thereto is low and imparting a large attenuation amount to said signal supplied thereto when the level of said signal supplied thereto is high, said second signal level adjusting means being coupled to receive an input signal from said transmission system means, and second control circuit means for generating said second control signal in response to the level of signal from said second signal level adjusting means.

Claim 18

A compressing and expanding circuit comprising means for amplifying an input signal; means comprising a control element having an impedance value which varies in response to a control signal; control circuit means for generating said control signal in response to the level of a signal applied thereto; switching means for switching over a signal path during compression periods so that an output signal from said amplifier is fed to said control circuit means as the signal applied to said control circuit means, and said control element is connected to the input side of said amplifier, and during expansion periods, an input signal to said amplifier is fed to said control circuit means as the signal applied to said control signal, said control element being connected to the negative feedback loop of said amplifier.

Claim 19

A compressing and expanding circuit comprising means for amplifying an input signal; means comprising a control element having an impedance value which varies in response to a control signal; control circuit means for generating said control signal in response to the level of a signal applied thereto; switching means for switching over a signal path during compression periods so that an output signal from said amplifier is fed to said control circuit means as the signal applied to said control circuit means, and said control element is connected to the input side of said amplifier, and during expansion periods, an input signal to said amplifier is fed to said control circuit means as the signal applied to said control signal, said control element being connected to the negative feedback loop of said amplifier.

Claim 20

A compressing and expanding circuit comprising: an amplifier for amplifying an input signal; a control element the resistance of which varies in response to a control signal applied thereto; a signal level adjusting circuit comprising at least one amplifier to which is connected a load circuit comprising linear circuit elements and non-linear circuit elements connected in series and imparting, with an input signal for a control signal, a small attenuation amount to said input signal when the level of said input signal is low and a large attenuation amount to said input signal when the level of said input signal is high; a control circuit for generating a control signal to be applied to said control element in response to the level of an input signal from said signal level adjusting circuit; and switching means for carrying out a signal path switchover operation such that, in compression periods, an output signal from said amplifier is fed to said adjusting circuit as an input signal for said control signal, and, further, said control element is connected to the input side of said amplifier, whereas, in expansion periods, an input signal to said amplifier is fed to said signal level adjusting circuit as an input signal for said control signal, said control element being connected to the negative feedback loop of said amplifier.

Claim 21

A compressing and expanding circuit comprising: an amplifier for amplifying an input signal; a control element the resistance of which varies in response to a control signal applied thereto; a signal level adjusting circuit comprising at least one amplifier to which is connected a load circuit comprising linear circuit elements and non-linear circuit elements connected in series and imparting, with an input signal for a control signal, a small attenuation amount to said input signal when the level of said input signal is low and a large attenuation amount to said input signal when the level of said input signal is high; a control circuit for generating a control signal to be applied to said control element in response to the level of an input signal from said signal level adjusting circuit; and switching means for carrying out a signal path switchover operation such that, in compression periods, an output signal from said amplifier is fed to said adjusting circuit as an input signal for said control signal, and, further, said control element is connected to the input side of said amplifier, whereas, in expansion periods, an input signal to said amplifier is fed to said signal level adjusting circuit as an input signal for said control signal, said control element being connected to the negative feedback loop of said amplifier.