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US 5,859,906 AGranted
Telephone switch hook interface circuit
AssigneeThomson Consumer Electronics, Inc.
InventorsRobert Alan Pitsch, James Edwin Hailey
Life of this patent
Estimating the term…
Abstract
A switch hook interface circuit couples a subscriber telephone to a subscriber telephone line. This interface circuit comprises a source of an off-hook signal, having one state indicating an off-hook condition, and a second state indicating an on-hook condition. A circuit is coupled between the off-hook signal source and the subscriber telephone line which gradually increases the current drawn from the subscriber telephone line when the off-hook signal indicates an off-hook condition, and gradually decreases the current drawn from the subscriber telephone line when the off-hook signal indicates an on-hook condition.
Claims13
A telephone switch hook interface circuit for coupling to a subscriber telephone line, comprising:
- a source of an off-hook signal, having a first state indicating an off-hook condition, and a second state indicating an on-hook condition;
- and
- a control circuit, coupled between the off-hook signal source and the subscriber telephone line, to gradually increase the current drawn from the subscriber telephone line from a minimum current to a maximum current when the off-hook signal indicates an off-hook condition, and gradually decrease the current drawn from the subscriber telephone line from the maximum current to the minimum current when the off-hook signal indicates an on-hook condition.
A telephone switch hook interface circuit for coupling to a subscriber telephone line, comprising:
- a source of an off-hook signal, having a first state indicating an off-hook condition and a second state indicating an on-hook condition;
- and
- a control circuit, coupled between the off-hook signal source and the subscriber telephone line, to gradually increase the current drawn from the subscriber telephone line from a minimum current to a maximum current when the off-hook signal indicates an off-hook condition, and gradually decrease the current drawn from the subscriber telephone line from the maximum current to the minimum current when the off-hook signal indicates an on-hook condition and wherein:
- the interface circuit further comprises a source of an enable signal having a first state indicating that the control circuit is to be enabled, and a second state indicating that the control circuit is to be disabled;
- the control circuit operates in one of an enabled and a disabled state, in response to the state of the enable signal, wherein:
- in the enabled state the control circuit gradually increases the current drawn from the subscriber telephone line from the minimum current to the maximum current when the off-hook signal indicates an off-hook condition, and gradually decreases the current drawn from the subscriber telephone line from the maximum current to the minimum current when the off-hook signal indicates an on-hook condition;
- and
- in a disabled state the control circuit switches the current drawn from the subscriber telephone line from the minimum current to the maximum current when the off-hook signal indicates an off-hook condition and switches the current drawn from the subscriber telephone line from the maximum current to the minimum current when the off-hook signal indicates an on-hook condition.
5 more elements
A telephone switch hook interface circuit for coupling to a subscriber telephone line, comprising:
- a source of an off-hook signal, having a first state indicating an off-hook condition and a second state indicating an on-hook condition;
- and
- a control circuit, coupled between the off-hook signal source and the subscriber telephone line, to gradually increase the current drawn from the subscriber telephone line from a minus current to a maximum current when the off-hook signal indicates an off-hook condition, and gradually decrease the current drawn from the subscriber telephone line from the maximum current to the minimum current when the off-hook signal indicates an on-hook condition and wherein the control circuit comprises:
- an amplifying circuit coupled to the subscriber telephone line, for varying the current drawn from the subscriber telephone line in response to a control signal;
- and
- a circuit for generating the control signal for controlling the amplifying circuit to gradually increase the current drawn from the subscriber telephone line in response to the off-hook signal indicating an off-hook condition and for controlling the amplifying circuit to gradually decrease the current drawn from the subscriber telephone line in response to the off-hook signal indicating an on-hook condition;
- and wherein:
- the amplifying circuit comprises a serial connection of a solid state relay and a main conduction path of a transistor, biased to operate as an amplifier, coupled between a source of operating potential and a source of reference potential;
- and
- the control signal generating means is coupled to a control electrode of the transistor.
7 more elements
A telephone switch hook interface circuit for coupling to a subscriber telephone line, comprising:
- a source of an off-hook signal, having a first state indicating an off-hook condition and a second state indicating an on-hook condition;
- and
- a control circuit, coupled between the off-hook signal source and the subscriber telephone line, to gradually increase the current drawn from the subscriber telephone line from a minimum current to a maximum current when the off-hook signal indicates an off-hook condition, and gradually decrease the current drawn from the subscriber telephone line from the maximum current to the minimum current when the off-hook signal indicates an on-hook condition and wherein the control circuit comprises:
- an amplifying circuit coupled to the subscriber telephone line, for varying the current drawn from the subscriber telephone line in response to a control signal;
- and
- a circuit for generating the control signal for controlling the amplifying circuit to gradually increase the current drawn from the subscriber telephone line in response to the off-hook signal indicating an off-hook condition and for controlling the amplifying circuit to gradually decrease the current drawn from the subscriber telephone line in response to the off-hook signal indicating an on-hook condition;
- and wherein:
- the control signal generating circuit comprises a resistor and capacitor coupled to the off-hook signal source for gradually charging the capacitor in response to the off-hook signal indicating an off-hook condition and gradually discharging the capacitor in response to the off-hook signal indicating an on-hook condition and using a voltage across the capacitor as the control signal;
- and wherein the control signal generating circuit further comprises:
- a serial connection of the resistor and the capacitor having a first and second terminal, wherein the first terminal of the serial connection is coupled to a source of reference potential;
- and
- a switch, for selectively coupling the second terminal of the serial connection to the source of reference potential in response to the off-hook signal indicating an on-hook condition and to a source of operating potential in response to the off-hook signal indicating an off-hook condition.
9 more elements
Dependencies are inferred from the claim text.