Circuit for comparing at least two input signals to generate control signals

Claim 2

A loud-speaking telephone system including: detecting means for detecting, transmitting and receiving voice signals; transmitting and receiving variable attenuators; and, circuit means for comparing signals detected by said detecting means to generate control signals for said variable attenuators, said circuit means comprising first and second input terminals connected to said detecting means, first and second output terminals connected to said attenuators, a first transistor circuit connected to said first input terminals and to said first output terminals, a second transistor connected to said second input terminals and said second output terminals, first means for turning said second transistor off when said first transistor is conductive, and second means for turning said first transistor off when said second transistor is conductive, whereby the respective amounts of attenuation of said attenuators are controlled in accordance with said control signals.

Claim 3

A loud-speaking telephone system as in claim 1, further comprising: a voltage supply and a source of reference potential adapted to be coupled to said circuit means.

Claim 4

A loud-speaking telephone system as in claim 2, wherein said circuit means further comprises: first and second series connected resistors connected between said first input terminal and the base of said first transistor, a third resistor connected between said voltage supply and the collector of said first transistor, and a fourth resistor connected between the collector of said first transistor and said reference potential, said collector of said first transistor being connected to said first output terminal, the emitter electrode of said first transistor being connected to said reference potential.

Claim 5

A loud-speaking telephone system as in claim 3, wherein said circuit means further comprises: fifth and sixth series connected resistors connected between said second input terminal and the base of said second transistor, a seventh resistor connected between said voltage supply and the collector of said second transistor and an eighth resistor connected between the collector of said second transistor and said reference potential, said collector electrode of said second transistor being connected to said second input terminal, the emitter of said second transistor being connected to said reference potential; a first diode connected to a junction between said first and second resistors and the collector of said second transistor; and a second diode connected to the junction between said fifth and sixth resistors and the collector electrode of said first transistor.

Claim 6

A loud-speaking telephone system as in claim 3, wherein said circuit means further comprises: fifth and sixth series connected resistors connected between said second input terminal and the base of said second transistor, the collector of said second transistor being connected to said output terminal and a junction between said first and second resistors, the emitter of said second transistor being connected to said reference potential; and a diode connected between a junction between said fifth and sixth resistors and the collector of said first tRansistor.

Claim 7

A loud-speaking telephone system as in claim 2, wherein said circuit means comprises; first and second series connected resistors connected between said first input terminal and the base of said first transistor, a junction between said first and second resistors being connected to said second input terminal, a third resistor connected between said voltage supply and the collector of said first transistor, and a fourth resistor connected between the collector of said first transistor and said reference potential, said collector electrode of said first transistor being connected to said first output terminal, the emitter of said transistor being connected to said reference potential; fifth and sixth series connected resistors connected between said second input terminal and the base of said second transistor, and a seventh resistor connected between said voltage supply and the collector of said second transistor, the emitter of said second transistor being connected to said reference potential; a first diode connected between a junction between said resistors and the collector of said second transistor; and a second diode connected to the junction between said fifth and sixth resistors and the collector of said first transistor.

Claim 8

A loud-speaking telephone system as in claim 3, wherein said circuit means further comprises: fifth and sixth series connected resistors connected between said second input terminal and the base of said second transistor, and a seventh resistor connected between said voltage supply and the collector of said second transistor, the emitter of said second transistor being connected to said reference potential; a first diode connected between a junction between said first and second resistors and the collector of said second transistor; and a second diode connected to the junction between said fifth and sixth resistors and the collector of said first transistor.

Claim 9

A loud-speaking telephone system as in claim 2, wherein said circuit means comprises: first and second series connected resistors connected between said first input terminal and the base of said first transistor, the collector of said first transistor being connected to said first output terminal, the emitter of said first transistor being connected to said reference potential; and, third and fourth series connected resistors connected between said second input terminal and the base of said second transistor, the collector of said second transistor being connected to said second input terminal and the junction between said first and second resistors, the emitter of said second transistor being connected to said reference potential, the junction between said third and fourth resistors being connected to the collector of said first transistor.

Claim 10

A loud-speaking telephone system as in claim 2, wherein said circuit means comprises: first and second series connected resistors connected between said first input terminal and the base of said first transistor, and a third resistor connected between said voltage supply and the collector of said first transistor; a second voltage supply, fourth and fifth series resistors connected between said second input terminals and the base of said second transistor, and a sixth resistor connected between said second voltage supply and the collector of said second transistor, the emitter of said second transistor being connected to the collector electrode of said first transistor, a first diode connected to a junction between said first and second resistors and said second output terminals; a second diode connected between said first output terminal and the collector of said first transistor, a third diode connected to the junction between said fourth and fifth resistors and said first output terminal; and a fourth diode connected between said second output terminal and the collector of said second transistor.

Claim 11

A loud-speaking telephone system as in claim 2, Wherein said circuit means comprises: first and second series connected resistors connected between said first input terminal and the base of said first transistor, and a third resistor connected between said voltage supply and the collector of said first transistor, said collector of said first transistor being connected to said first output terminal, the emitter of said first transistor being connected to said reference potential; a second voltage supply; fourth and fifth series connected resistors connected between said second input terminal and the base of said second transistor, and a sixth resistor connected between said second voltage supply and the collector of said second transistor, the emitter of said second transistor being connected to said reference potential; a first diode connected to a junction between said first and second resistors and the collector of said second transistor; and a second diode connected to a junction between said fourth and fifth resistors and the collector of said first transistor.