Compressor/expander switching methods and apparatus

Claim 2

A selectively switchable signal compressor/expander comprising a main path extending between an input terminal and a first output terminal and including means for combining a further signal with the signal in said main path, a further path having an input and output for Providing said further signal, first connecting means operative to establish a first connection in which said further path input is connected to a point in said main path and said further path output is connected to said combining means for establishing a compressor configuration whereby said further signal boosts said signal in said main path, second connecting means operative to establish a second connection in which said further path input is connected to a point in said main path and said further path output is connected to said combining means for establishing an expander configuration whereby said further signal bucks said signal in said main path, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels, switching means for rendering said first connecting means effective and said second connecting means ineffective in a compressor mode and for rendering said first connecting means ineffective and said second connecting means effective in an expander mode, and a terminal connected to said input of said further path.

Claim 3

A compressor/expander according to claim 1, in which the signals at said further path input and output are subtractively combined and fed to an output terminal.

Claim 4

A compressor/expander according to claim 1, in which switch means are provided for rendering said further signal ineffective, whereby signals are transferred from said input terminal to one or more output terminals in a substantially proportional manner.

Claim 5

A compressor/expander according to claim 1, wherein said first connecting means connect said further path input to a first point in said main path preceding said combining means and said second connecting means connect said further path input to a second point in said main path following said combining means.

Claim 6

A compressor/expander according to claim 4, wherein the signal path polarities are arranged such that the signals in said combining means combine additively when said first connecting means is effective and subtractively when said second connecting means is effective.

Claim 7

A compressor/expander according to claim 4, wherein the connection of said further path output to said combining means is by way of a permanent connection effective in both said first and second connections, and said switching means comprise a single-pole, two-way switch for connecting said further path input selectively to said first or second point.

Claim 8

A compressor/expander according to claim 6, comprising a further single-pole, two-way switch for connecting said input terminal selectively to a terminal for receiving a signal to be recorded or to a terminal for receiving a playback signal, said single-pole switches being ganged.

Claim 9

A compressor/expander according to claim 1, wherein said combining means comprise first combining means followed by second combining means, said first connecting means connect said further path output to one of said first and second combining means, said second connecting means connect said further path output to the other of said first and second combining means, and both said connecting means connect said further path input to a point between said first and second combining means.

Claim 10

A compressor/expander according to claim 8, wherein the connection of said further path input to said point between said first and second combining means is by way of a permanent connection effective in both said first and second connections.

Claim 11

A compressor/expander according to claim 9, wherein said switching means comprises a single-pole, two-way switch for connecting said further path output selectively to said first or said second combining means.

Claim 12

A compressor/expander according to claim 10, wherein said switching means comprise a second single-pole, two-way switch ganged to the switch recited in claim 10 for grounding the connection to the non-selected combining means.

Claim 13

A compressor/expAnder according to claim 10, comprising a further single-pole, two-way switch for connecting said input terminal selectively to a terminal for receiving a signal to be recorded or to a terminal for receiving a playback signal, said single-pole switches being ganged.

Claim 14

A compressor/expander according to claim 9, wherein said connection means include first and second permanent connections from said further path output to said first and second combining means respectively, and said switching means comprise a single-pole, two-way switch for selectively clamping at least one of said permanent connections to a reference potential.

Claim 15

A compressor/expander according to claim 13 comprising a further single-pole, two-way switch for connecting said input terminal selectively to a terminal for receiving a signal to be recorded or to a terminal for receiving a playback signal, said single-pole switches being ganged.

Claim 16

A compressor/expander according to claim 8, wherein said connecting means connect said further path output permanently to said first and second combining means, wherein said main path is interrupted between said first and second combining means wherein one input of said second combining means is connected to said further path input, wherein a second input terminal is provided, and wherein said switching means comprise a single-pole, two-way switch for selectively connecting said further path input to the output of said first combining means and to said second input terminal.

Claim 17

A selectively switchable signal compressor/expander comprising a main path extending between an input terminal and a first output terminal and including means for combining a further signal with the signal in said main path, a further path having an input and output for providing said further signal connecting means connecting said further path output to said combining means, and switching means for selectively connecting said further path input to one of said input and output terminals for establishing a compressor configuration whereby said further signal boosts said signal in said main path, or for connecting said further path input to the other of said input and output terminals for establishing an expander configuration whereby said further signal bucks said signal in said main path, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels.

Claim 18

A selectively switchable signal compressor/expander comprising a main path extending between an input terminal and a first output terminal and including means for combining a further signal with the signal in said main path, a further path having an input and output for providing said further signal connecting means connecting said further path output to said combining means, and switching means for selectively connecting said further path input to one of said input and output terminals for establishing a compressor configuration whereby said further signal boosts said signal in said main path, or for connecting said further path input to the other of said input and output terminals for establishing an expander configuration whereby said further signal bucks said signal in said main path, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels.

Claim 19

A compressor/expander according to claim 16, wherein the signal path polarities are arranged such that the signals in said combining means combine additively when said input is selectively connected to said input terminal and subtractively when said input is selectively connected to said output terminal.

Claim 20

A compressor/expander according to claim 17, further comprising a second output terminal connected to said input of said further path.

Claim 21

A compressor/expander according to claim 16, wherein the signal path polarities are arranged such that the signals in said combining means combine additively when said input is selectively connected to said output terminal and subtractively when said input is selectively connected to said input terminal.

Claim 22

A compressor/expander according to claim 19, comprising a further output terminal which is connected to the output of a combining means which subtractively combines the signals at said further path input and said further path output.

Claim 23

A compressor/expander according to claim 16, comprising a further switching means for connecting said input terminal selectively to a terminal for receiving a signal to be recorded or to a terminal for receiving a playback signal, said switching means being ganged.

Claim 24

A selectively switchable signal compressor/expander comprising a main path extending between an input terminal and a first output terminal and including a first followed by a second combining means for combining a further signal with the signal in said main path, A further path having an input and an output for providing said further signal, connecting means connecting said further path input to a point in said main path between said combining means, switching means for selectively connecting said further path output to one of said combining means for establishing a compressor configuration whereby said further signal boosts said signal in said main path or for connecting said further path output to the other of said combining means for establishing an expander configuration whereby said further signal bucks said signal in said main path, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels, and a second output terminal connected to said input of said further path.

Claim 25

A selectively switchable signal compressor/expander comprising a main path extending between an input terminal and a first output terminal and including a first followed by a second combining means for combining a further signal with the signal in said main path, A further path having an input and an output for providing said further signal, connecting means connecting said further path input to a point in said main path between said combining means, switching means for selectively connecting said further path output to one of said combining means for establishing a compressor configuration whereby said further signal boosts said signal in said main path or for connecting said further path output to the other of said combining means for establishing an expander configuration whereby said further signal bucks said signal in said main path, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels, and a second output terminal connected to said input of said further path.

Claim 26

A compressor/expander according to claim 22, wherein the signal path polarities are arranged such that the signals in said first combining means combine subtractively and in the second additively.

Claim 27

A compressor/expander according to claim 22, wherein the signal path polarities are arranged such that the signals in said first combining means combine additively and in the second subtractively.

Claim 28

A signal compressor/expander according to claim 24, wherein the further signal input of said second combining means is connected to the output of said further path.

Claim 29

A compressor/expander according to claim 22, comprising further switching means for connecting said input terminal selectively to a terminal for receiving a signal to be recorded or to a terminal for receiving a playback signal, said switching means being ganged.

Claim 30

A selectively switchable signal compressor/expander comprising first and second input terminals, first and second output terminals, first combining means having a first input connected to said first input terminal, a further path having an input and output, first connecting means connecting said further path output to the second input of said first combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signals in said first combining means combine subtractively, second combining means with a first input, second connecting means connecting said further path output to the second input of said second combining means for establishing a compressor configuration whereby the signals in said second combining means combine subtractively, said further path having signal level restricting characteristics above a low-level threshold, such that the boosting and bucking actions produced are significant only at low input signal levels, and switching means for connecting said further path input selectively to said second input terminal or to the output of said first combining means, said first and second output terminals being connected respectively to said further path input and the output of said second combining means, and said first input of said second combining means being connected to a point which, at least in compression mode, is the same as said input.

Claim 31

A selectively switchable signal compressor/expander comprising first and second input terminals, first and second output terminals, first combining means having a first input connected to said first input terminal, a further path having an input and output, first connecting means connecting said further path output to the second input of said first combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signals in said first combining means combine subtractively, second combining means with a first input, second connecting means connecting said further path output to the second input of said second combining means for establishing a compressor configuration whereby the signals in said second combining means combine subtractively, said further path having signal level restricting characteristics above a low-level threshold, such that the boosting and bucking actions produced are significant only at low input signal levels, and switching means for connecting said further path input selectively to said second input terminal or to the output of said first combining means, said first and second output terminals being connected respectively to said further path input and the output of said second combining means, and said first input of said second combining means being connected to a point which, at least in compression mode, is the same as said input.

Claim 32

A selectively switchable signal compressor/expander comprising first and second input terminals, first and second output terminals, first combining means having a first input connected to said first input terminal, a further path having an input and output, first connecting means connecting said further path output to the second input of said first combining means for establishing a compressor configuration whereby the signal path polarities are so arranged that the signals in said first combining means combine additively, second combining means with a first input connected to said input, second connecting means connecting said further path output to the second input of said second combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signals in said second combining means combine subtractively, said further path having signal Level restricting characteristics above a low-level threshold such that the boosting and bucking actions produced are significant only at low input signal levels, and switching means for connecting said further path input selectively to said second input terminal or to the output of said first combining means, said second output terminal being connected to the output of said second combining means, and said first output terminal being connected to a point which, at least in compression mode, is the same as said input.

Claim 33

A selectively switchable signal compressor/expander comprising first and second input terminals, first and second output terminals, first combining means having a first input connected to said first input terminal, a further path having an input and output, first connecting means connecting said further path output to the second input of said first combining means for establishing a compressor configuration whereby the signal path polarities are so arranged that the signals in said first combining means combine additively, second combining means with a first input connected to said input, second connecting means connecting said further path output to the second input of said second combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signals in said second combining means combine subtractively, said further path having signal Level restricting characteristics above a low-level threshold such that the boosting and bucking actions produced are significant only at low input signal levels, and switching means for connecting said further path input selectively to said second input terminal or to the output of said first combining means, said second output terminal being connected to the output of said second combining means, and said first output terminal being connected to a point which, at least in compression mode, is the same as said input.

Claim 34

A selectively switchable signal compressor/expander comprising a main path extending between an input terminal and a first output terminal and including a first followed by a second means for combining a further signal with the signal in said main path, a further path having an input and an output for providing said further signal, first connecting means connecting said input to a point in said main path between said combining means, second connecting means connecting said output to one of said combining means for establishing a compressor configuration whereby said further signal boosts said signal in said main path, third means connecting said output to the other of said combining means for establishing an expander configuration whereby said further signal bucks said signal in said main path, said further path having signal level restricting characteristics, above a low-level threshold such that said boosting and bucking are significant only at low input signal levels, and switching means for selectively grounding at least one of said second or said third connecting means.

Claim 35

A selectively switchable signal compressor/expander comprising a main path extending between an input terminal and a first output terminal and including a first followed by a second means for combining a further signal with the signal in said main path, a further path having an input and an output for providing said further signal, first connecting means connecting said input to a point in said main path between said combining means, second connecting means connecting said output to one of said combining means for establishing a compressor configuration whereby said further signal boosts said signal in said main path, third means connecting said output to the other of said combining means for establishing an expander configuration whereby said further signal bucks said signal in said main path, said further path having signal level restricting characteristics, above a low-level threshold such that said boosting and bucking are significant only at low input signal levels, and switching means for selectively grounding at least one of said second or said third connecting means.

Claim 36

A compressor/expander according to claim 29, further comprising a second output terminal connected to said input of said further path.

Claim 37

A compressor/expander according to claim 29, wherein the signal path polarities are arranged such that the signals in said first combining means combine subtractively and in the second additively.

Claim 38

A compressor/expander according to claim 29, wherein the signal path polarities are arranged such that the signals in said first combining means combine additively and in the second subtractively.

Claim 39

A circuit for use with a tape recorder comprising a selectively switchable signal compressor-expander comprising a first terminal for receiving an input signal, a second terminal for receiving a signal played back from the recorder, a third terminal, first switching means for selectively connecting said third terminal to said first terminal or said second terminal, a fourth terminal, combining means connected between said third and fourth terminals, a further path having an input and an output, a fifth terminal connected to said input, a recording amplifier connected to one of said fourth terminal and a point which, at least in compression mode, is the same as said fifth terminal, the other of said fourth and fifth terminals providing a monitoring terminal, first connecting means operative to establish a first connection in which said further path input is connected to a point between said third and fourth terminals and said further path output is connected to said combining means for establishing a compressor configuration whereby the signal path polarities are so arranged that the signal from said further path boosts the signal at one of said fourth and fifth terminals, second connecting means operative to establish a second connection in which said further path input is connected to a point between said third and fourth terminals and said further path output is connected to said combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signal from said further path bucks the signal at one of said fourth and fifth terminals, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels, and second switching means ganged to said first switching means for renderIng said first connecting means effective and said second connecting means ineffective in a compressor mode and for rendering said first connecting means ineffective and said second connecting means effective in an expander mode.

Claim 40

A circuit for use with a tape recorder comprising a selectively switchable signal compressor-expander comprising a first terminal for receiving an input signal, a second terminal for receiving a signal played back from the recorder, a third terminal, first switching means for selectively connecting said third terminal to said first terminal or said second terminal, a fourth terminal, combining means connected between said third and fourth terminals, a further path having an input and an output, a fifth terminal connected to said input, a recording amplifier connected to one of said fourth terminal and a point which, at least in compression mode, is the same as said fifth terminal, the other of said fourth and fifth terminals providing a monitoring terminal, first connecting means operative to establish a first connection in which said further path input is connected to a point between said third and fourth terminals and said further path output is connected to said combining means for establishing a compressor configuration whereby the signal path polarities are so arranged that the signal from said further path boosts the signal at one of said fourth and fifth terminals, second connecting means operative to establish a second connection in which said further path input is connected to a point between said third and fourth terminals and said further path output is connected to said combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signal from said further path bucks the signal at one of said fourth and fifth terminals, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels, and second switching means ganged to said first switching means for renderIng said first connecting means effective and said second connecting means ineffective in a compressor mode and for rendering said first connecting means ineffective and said second connecting means effective in an expander mode.

Claim 41

A circuit according to claim 33, wherein said first connecting means connect said further path input to a first point in said main path preceding said combining means and said second connecting means connect said further path input to a second point in said main path following said combining means.

Claim 42

A circuit according to claim 34, wherein said first connecting means connect said further path input to a first point in said main path following said combining means and said second connecting means connect said further path input to a second point in said main path preceding said combining means.

Claim 43

A circuit according to claim 35, comprising a monitoring output terminal which is connected to the output of a combining means which subtractively combines the signals at said further path input and output.

Claim 44

A circuit according to claim 34, wherein said second switching means selectively connect said further path input to said first or said second point.

Claim 45

A circuit according to claim 35, wherein said second switching means selectively connect said further path input to said first or said second point.

Claim 46

A circuit according to claim 33, wherein said combining means comprise first combining means followed by second combining means, said first connecting means connect said further path output to one of said first and second combining means, said second connecting means connect said further path output to the other of said first and second combining means, and both said connecting means connect said input to a point between said first and second combining means.

Claim 47

A circuit according to claim 39, comprising a monitoring output terminal which is connected to the output of a combining means which subtractively combines the signals at said further path input and output.

Claim 48

A circuit according to claim 39, wherein the connection of said further path input to said point between said first and second combining means is by way of a permanent connection effective in both said first and second connections.

Claim 49

A circuit according to claim 41, wherein said switching means comprise a single-pole, two-way switch for connecting said further path output selectively to said first or said second combining means.

Claim 50

A circuit according to claim 42, wherein said switching means comprise a second single-pole, two-way switch ganged to the switch recited in claim 42 for grounding the further signal connection to at least the said first combining means.

Claim 51

A circuit according to claim 41, wherein said connecting means include first and second permanent connections from said further path output to said first and second combining means respectively, and said switching means comprise a single-pole, two-way switch for selectively clamping at least said first permanent connection to a reference potential.

Claim 52

A circuit for use with a tape recorder comprising a selectively switchable signal compressor/expander comprising a first terminal for receiving an input signal, a second terminal for receiving a signal played back from the recorder, first and second combining means, a third terminal connected to the output of said second combining means, a further path having an input and an output, an input of said second combining means connected to said further path input, a recording amplifier connected to one of said third terminal and a fourth terminal, the other of said third and fourth terminals providing a monitoring output terminal, first connecting means connecting said further path output to one of said combining means for establishing a compressor configuration whereby the signal path polarities are so arranged that the signal from said further path boosts the signal at one of said third and fourth terminals, second connecting means connEcting said further path output to the other of said combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signal from said further path bucks the signal at one of said third and fourth terminals, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels, switching means selectively connecting said further path input to one of said first and second input terminals or the output of said first combining means, the other of said first and second terminals being connected to an input of said first combining means, and said fourth terminal being connected to said further path input at least in one setting of said switching means.

Claim 53

A circuit for use with a tape recorder comprising a selectively switchable signal compressor/expander comprising a first terminal for receiving an input signal, a second terminal for receiving a signal played back from the recorder, first and second combining means, a third terminal connected to the output of said second combining means, a further path having an input and an output, an input of said second combining means connected to said further path input, a recording amplifier connected to one of said third terminal and a fourth terminal, the other of said third and fourth terminals providing a monitoring output terminal, first connecting means connecting said further path output to one of said combining means for establishing a compressor configuration whereby the signal path polarities are so arranged that the signal from said further path boosts the signal at one of said third and fourth terminals, second connecting means connEcting said further path output to the other of said combining means for establishing an expander configuration whereby the signal path polarities are so arranged that the signal from said further path bucks the signal at one of said third and fourth terminals, said further path having signal level restricting characteristics above a low-level threshold, such that said boosting and bucking are significant only at low input signal levels, switching means selectively connecting said further path input to one of said first and second input terminals or the output of said first combining means, the other of said first and second terminals being connected to an input of said first combining means, and said fourth terminal being connected to said further path input at least in one setting of said switching means.