Compression and/or expansion system and circuit

Claim 2

A compression system comprising first frequency characteristic change means having a specific fixed frequencyresponse characteristic which increases the level of an input signal in a predetermined frequency band, second frequency characteristic change means in a series connection with said first frequency characteristic change means and having a variable frequency-response characteristic which varies between a characteristic complementary with the frequency-response characteristic of said first frequency characteristic change means and a flat characteristic, control means for generating a control signal in accordance with the level of the input signal, means for supplying the control signal to said second frequency characteristic change means for controlling the characteristic of said second frequency characteristic change means, and means whereby said change approaches said complementary characteristic as said level of the input signal becomes larger and approaches said flat characteristic as said level of the input signal becomes smaller.

Claim 3

The compression system as defined in claim 1 in which said control means comprises filter means for filtering a signal of said predetermined fRequency band in the input signal, and signal level detection means for detecting the level of the signal filtered by said filter means and thereby generating said control signal.

Claim 4

THe compression system as defined in claim 1 in which said first frequency characteristic change means has fixed frequency-response characteristics which increase the level of the input signal in a plurality of different predetermined frequency bands, and said second frequency characteristic change means has variable frequency-response characteristics which vary between characteristics, each of said characteristics being complementary with each corresponding frequency-response characteristic of said first frequency characteristic change means for said plurality of frequency bands and a flat characteristic.

Claim 5

The compression system as defined in claim 1 in which said first frequency characteristic change means comprises a plurality of fixed frequency characteristic change means which respectively have fixed frequency-response characteristics which increase the level of the input signal in different predetermined frequency bands, said second frequency characteristic change means comprises a plurality of variable frequency characteristic change means having variable frequency-response characteristics which vary between characteristics each of which is complementary with the frequency-response characteristic of the corresponding fixed frequency characteristic change means and a flat characteristic, and said control means comprises a plurality of control circuit means which apply a control signal to each corresponding variable frequency characteristic change means in accordance with the level of the signal in each corresponding predetermined frequency band.

Claim 6

The compression system as defined in claim 1 in which said first frequency characteristic change means comprises a single fixed frequency characteristic change means which has a fixed frequency-response characteristic which increases the level of the input signal in a plurality of different predetermined frequency bands, said second frequency characteristic change means comprises a plurality of variable frequency characteristic change means having variable frequency-response characteristics which vary between characteristics each of which is complimentary with each corresponding frequency-response characteristic of said fixed frequency characteristic change means and a flat characteristic, and said control means comprises a plurality of control circuit means which apply a control signal to each corresponding variable frequency characteristic change means in accordance with the level of the signal in each corresponding predetermined frequency band.

Claim 7

An expansion system for expanding the signal compressed by the compression system as defined in claim 1, said expansion system comprising third frequency characteristic change means having a specific fixed frequency-response characteristic which are complementary with said characteristic of said first frequency characteristic change means which decreases the level of the signal in said predetermined frequency band, fourth frequency characteristic change means connected in a series relationship with said third frequency characteristic change means and having a variable frequency-response characteristic which varies between a characteristic which is complementary with the frequency-response characteristic of said third frequency characteristic change means and a flat characteristic, and second control means for generating a control signal in accordance with the level of the signal, means for supplying the control signal to said fourth frequency characteristic change means for controlling the characteristic of said fourth frequency characteristic change means so that it approaches said complementary characteristic as said level of the signal becomes larger and approaches said flat characteristic as said level of the signal becomes smaller.

Claim 8

The expansion system as defined in claim 6 In which said second control means comprises filter means for filtering a signal of said predetermined frequency band in the input signal to said means and signal level detection means for detecting the level of the signal filtered by said filter means and thereby generating said control signal.

Claim 9

An expansion system for expanding the signal compressed by the compression system as defined in claim 3, said expansion system comprising third frequency characteristic change means having a fixed frequency-response characteristic respectively complementary with the corresponding characteristics in a plurality of mutually different predetermined frequency bands of said first frequency characteristic change means which decrease the level of the signal in said predetermined frequency band, fourth frequency characteristic change means connected in a series relation with said third frequency characteristic change means and having a variable frequency-response characteristic which varies between characteristic limits, each of said limits being complementary with the frequency-response characteristic in the corresponding frequency band of said third frequency characteristic change means and a flat characteristic, and second control means for generating a control signal in accordance with the level of the signal, means for supplying the control signal to said fourth frequency characteristic change means and controlling the characteristic of said fourth characteristic change means so that it approaches said complementary characteristic as said level of the signal becomes larger and approaches said flat characteristic as said level of the signal becomes smaller.

Claim 10

The expansion system as defined in claim 8 in which said fourth frequency characteristic change means comprises a plurality of variable frequency characteristic change means each having variable frequency-response characteristics which vary between characteristic limits each of which is complementary with the frequency-response characteristic in the corresponding frequency band of said fixed frequency characteristic change means and a flat characteristic, and said control means comprises a plurality of control circuit means each of which applies a control signal to each corresponding variable frequency characteristic change means in accordance with the level of the signal in each corresponding predetermined frequency band.

Claim 11

The expansion system as defined in claim 9 in which each of said control circuit means comprises filter means having a passing band different from each other, and signal level detection means for detecting the level of the signal filtered by said respective filter means and thereby generating said control signal.

Claim 12

The expansion system as defined in claim 9 in which said third frequency characteristic change means comprises a plurality of fixed frequency characteristic change means which respectively have fixed frequency-response characteristics which decrease the level of the input signal in different predetermined frequency bands.

Claim 13

The expansion system as defined in claim 9 in which said third frequency characteristic change means comprises a single fixed frequency characteristic change means which has a fixed frequncy-response characteristic which decreases the level of the input signal in different predetermined frequency bands.

Claim 14

A compression circuit comprising first frequency characteristic change circuit means having a specific fixed frequency-response characteristic which increases the level of an input signal in a predetermined frequency band, second frequency characteristic change circuit means in series connection with said first frequency characteristic change circuit means, said second circuit means having a variable frequency-response characteristic which varies between a characteristic complementary with the frequency-response characteristic of said first frequency characteristic change circuit means and a flat characteristic, control circuit means for generating a Control signal in accordance with the level of the input signal, and means for supplying the control signal to said second frequency characteristic change circuit means, said control signal controlling the characteristic of said second frequency characteristic change circuit means so that said characteristics approach said complementary characteristic as said level of the input signal becomes larger and approaches said flat characteristic as said level of the input signal becomes smaller.

Claim 15

A compression circuit comprising first frequency characteristic change circuit means having a specific fixed frequency-response characteristic which increases the level of an input signal in a predetermined frequency band, second frequency characteristic change circuit means in series connection with said first frequency characteristic change circuit means, said second circuit means having a variable frequency-response characteristic which varies between a characteristic complementary with the frequency-response characteristic of said first frequency characteristic change circuit means and a flat characteristic, control circuit means for generating a Control signal in accordance with the level of the input signal, and means for supplying the control signal to said second frequency characteristic change circuit means, said control signal controlling the characteristic of said second frequency characteristic change circuit means so that said characteristics approach said complementary characteristic as said level of the input signal becomes larger and approaches said flat characteristic as said level of the input signal becomes smaller.

Claim 16

The compression circuit as defined in claim 13 in which said control circuit means comprises a filter means for filtering a signal of said predetermined frequency band in the input signal, and signal level detection circuit means for detecting the level of the signal filtered by said filter and thereby generating said control signal.

Claim 17

The compression circuit as defined in claim 13 which further comprises a transistor the emitter of which is grounded through an emitter resistor, and in which said first frequency characteristic change circuit means includes a series circuit of a capacitor and a resistor connected in parallel with said emitter resistor, and said second frequency characteristic change circuit means includes a capacitor and a control element connected in series with each other between the collector of said transistor and the ground, said control element varying its impedance responsive to an application thereto of the control signal voltage from said control circuit.

Claim 18

The compression circuit as defined in claim 13 in which said first frequency characteristic change circuit means comprises a plurality of fixed frequency characteristic change circuit means which respectively have fixed frequency-response characteristics which increase the level of the input signal in different predetermined frequency bands, said second frequency characteristic change circuit means comprises a plurality of variable frequency characteristic change circuit means respectively having variable frequency-response characteristics which vary between characteristics, each of which is complementary with the frequency-response characteristic of the corresponding fixed frequency characteristic change circuit and a flat characteristic, said control circuit means comprises a plurality of control circuit means, each of which generates a control signal voltage in accordance with the level of the signal in each corresponding predetermined frequency band, and said each variable frequency characteristic change circuit means includes a control element which varies its impedance responsive to an application thereto of the control signal voltage from the corresponding control circuit.

Claim 19

The compression circuit as defined in claim 13 in which said first frequency characteristic change circuit means comprises a single fixed frequency characteristic change circuit means which has a fixed frequency-response characteristic which increases the level of the input signal in a plurality of different predetermined frequency bands, said second frequency characteristic change circuit means comprises a plurality of variable frequency characteristic change circuit means respectively having variable frequency-response characteristics which vary between characteristics each of which is complementary with the frequency-response characteristic of the corresponding frequency band of said fixed frequency characteristic change circuit means and a flat characteristic, and said each variable frequency characteristic change circuit means includes a control element which varies its impedance in response to an application thereto of the control signal voltage from the corresponding control circuit.

Claim 20

An expansion circuit for expanding the signal compressed by the compression circuit as defined in claim 6, said expansion circuit comprising a third frequency characteristic change circuit means having a specific fixed frequency-response characteristic which is complementary with said characteristic of said first Frequency characteristic change means which decreases the level of the signal in said predetermined frequency band, a fourth frequency characteristic change circuit means connected in a series relation with said third frequency characteristic change circuit and having a variable frequency-response characteristic which varies between a characteristic which is complementary with the frequency-response characteristic of said third frequency characteristic change circuit and a flat characteristic, and a second control circuit means for generating a control signal in accordance with the level of the input signal, supplying the control signal to said fourth frequency characteristic change circuit means and controlling the characteristic of said fourth frequency characteristic change circuit means so that it approaches said complementary characteristic as said level of the signal becomes larger and approaches said flat characteristic as said level of the signal becomes smaller.

Claim 21

The expansion circuit as defined in claim 18 in which said second control circuit comprises a filter for filtering a signal of said predetermined frequency band in the input signal to said circuit and a signal level detection circuit for detecting the level of the signal filtered by said filter and thereby generating said control signal.

Claim 22

The expansion circuit as defined in claim 18 which further comprises a transistor the emitter of which is grounded through an emitter resistor, and in which said third frequency characteristic change circuit means includes a capacitor and a resistor connected in series between the collector of said transistor and the ground, said fourth frequency characteristic change circuit means includes a series circuit of a capacitor and a control element which varies its impedance by an application thereto of the control signal voltage from said second control circuit, said series circuit being connected in parallel with said emitter resistor of said transistor.

Claim 23

An expansion circuit for expanding the signal compressed by the compressing circuit as defined in claim 13, said expansion circuit comprising a third frequency characteristic change circuit means having fixed frequency-response characteristics respectively complementary with the corresponding characteristics in a plurality of mutually different predetermined frequency bands of said first frequency characteristic change circuit means which decreases the level of the signal in said predetermined frequency band, a fourth frequency characteristic change circuit means connected in a series relation with said third frequency characteristic change circuit means and having variable frequency-response characteristics which vary between characteristic limits each of which is complementary with the frequency-response characteristic in the corresponding frequency band of said third frequency characteristic change circuit means and a flat characteristic, and a second control circuit means for generating a control signal in accordance with the level of the signal, means for supplying the control signal to said fourth frequency characteristic change circuit means for controlling the characteristic of said fourth frequency characteristic change circuit so that it approaches said complementary characteristic as said level of the signal becomes larger and approaches said flat characteristic as said level of the signal becomes smaller.

Claim 24

The expansion circuit as defined in claim 21 in which said third frequency characteristic change circuit means comprised a plurality of fixed frequency characteristic change circuits which respectively have fixed frequency-response characteristics which decrease the level of the input signal in different predetermined frequency bands.

Claim 25

The expansion circuit as defined in claim 21 in which said third frequency characteristic change circuit means comprises a single fixed frequency characteristic change circuit means which has a fixed frequency-response characteristic which decreases The level of the input signal in different predetermined frequency bands.

Claim 26

The expansion circuit as defined in claim 21 in which said fourth frequency characteristic change circuit means comprises a plurality of variable frequency characteristic change circuit means, each having variable frequency-response characteristics which vary between characteristic limits each of which is complementary with the frequency-response characteristic in the corresponding frequency band of said third frequency characteristic change circuit means and a flat characteristic, said control circuit means comprising a plurality of control circuits each of which generates a control signal voltage in accordance with the level of signal in the corresponding predetermined frequency band, and each of said plurality of variable frequency characteristic change circuit means includes a control element which varies its impedance by an application thereto of the control voltage from the corresponding control circuit of said plurality of control circuits.

Claim 27

The expansion circuit as defined in claim 24 in which each of said control circuits comprises a filter having a passing band different from each other and a signal level detector for detecting the level of the signal filtered by said filter and thereby generating said control signal.

Claim 28

A compression and expansion system comprising first frequency characteristic change means having a specific fixed frequency-response characteristic which increases the level of an input signal in a predetermined frequency band, second frequency characteristic change means connected in a series relation with said first frequency characteristic change means and having a variable frequency-response characteristic which varies between a characteristic which is complementary with the frequency-response characteristic of said first frequency characteristic change means and a flat characteristic, first control means for generating a control signal in accordance with the level of the input signal, means for supplying the control signal to said second frequency characteristic change means for cntrolling the characteristic of said second frequency characteristic change means so that it approaches said complementary characteristic as said level of the input signal becomes larger and approaches said flat characteristic as said level of the input signal becomes smaller, transmission system means for transmitting the signal compressed in said first and second frequency characteristic change means, third frequency characteristic change means having a specific fixed frequency-response characteristic complementary with said characteristic of said first frequency characteristic change means, said complementary characteristic decreasing the level of the signal transmitted through said transmission system means in said predetermined frequency band, fourth frequency characteristic change means connected in a series relationship with said third frequency characteristic change means and having a variable frequency-response characteristic which varies between a characteristic complementary with the frequency-response characteristic of said third frequency characteristic change means and a flat characteristic, and second control means for generating a control signal in accordance with the level of the signal, means for supplying the control signal to said fourth frequency characteristic change means for controlling the characteristic of said fourth frequency characteristic change means so that it approaches said complementary characteristic as said level of the signal becomes larger and approaches said flat characteristic as said level of the signal becomes smaller.

Claim 29

A compression and expansion system comprising first frequency characteristic change means having a specific fixed frequency-response characteristic which increases the level of an input signal in a predetermined frequency band, second frequency characteristic change means connected in a series relation with said first frequency characteristic change means and having a variable frequency-response characteristic which varies between a characteristic which is complementary with the frequency-response characteristic of said first frequency characteristic change means and a flat characteristic, first control means for generating a control signal in accordance with the level of the input signal, means for supplying the control signal to said second frequency characteristic change means for cntrolling the characteristic of said second frequency characteristic change means so that it approaches said complementary characteristic as said level of the input signal becomes larger and approaches said flat characteristic as said level of the input signal becomes smaller, transmission system means for transmitting the signal compressed in said first and second frequency characteristic change means, third frequency characteristic change means having a specific fixed frequency-response characteristic complementary with said characteristic of said first frequency characteristic change means, said complementary characteristic decreasing the level of the signal transmitted through said transmission system means in said predetermined frequency band, fourth frequency characteristic change means connected in a series relationship with said third frequency characteristic change means and having a variable frequency-response characteristic which varies between a characteristic complementary with the frequency-response characteristic of said third frequency characteristic change means and a flat characteristic, and second control means for generating a control signal in accordance with the level of the signal, means for supplying the control signal to said fourth frequency characteristic change means for controlling the characteristic of said fourth frequency characteristic change means so that it approaches said complementary characteristic as said level of the signal becomes larger and approaches said flat characteristic as said level of the signal becomes smaller.

Claim 30

A compression and expansion system comprising compression means for independently varying the level of an electrical signal in each of a plurality of predetermined frequency bands, said compression means varying the level of said electrical signal to compress said signal in a fixed frequency-response relationship, Expansion means for variably changing the level of said compressed electrical signal in each of said frequency bands in a manner which is complementary to the varying by said compression means, and means whereby the magnitude of the variance by said expansion means becomes larger as the level of the electrical signal becomes larger and becomes smaller as the level of the electrical signal becomes smaller.

Claim 31

A compression and expansion system comprising compression means for independently varying the level of an electrical signal in each of a plurality of predetermined frequency bands, said compression means varying the level of said electrical signal to compress said signal in a fixed frequency-response relationship, Expansion means for variably changing the level of said compressed electrical signal in each of said frequency bands in a manner which is complementary to the varying by said compression means, and means whereby the magnitude of the variance by said expansion means becomes larger as the level of the electrical signal becomes larger and becomes smaller as the level of the electrical signal becomes smaller.