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US 5,317,392 AGranted
Noise reducing device for up-going signals in bidirectional CATV system
AssigneeNEC Corporation
InventorsRyouji Ishibashi, Naomasa Nishimoto
Life of this patent
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Abstract
A device incorporated in a bidirectional CATV system for reducing noise introduced in an up-going channel at a subscriber station. A terminal unit and a protector perform monodirectional or bidirectional switching operations on the basis of a DC current which the terminal station selectively outputs.
Claims4
In a CATV system of the type having a central unit interconnected with a terminal unit, a noise reducing device for an up-going signal from the terminal unit to the central unit comprising:
- controller means at the terminal unit for superposing a DC current on an up-going signal only when said terminal unit sends an up-going signal to the central unit;
- high-pass filter means connected between the central unit and the terminal unit and passing only a down-going signal from the central unit to the terminal unit;
- bidirectional circuit means paralleling the high-pass filter means and passing both of an up-going signal and a down-going signal;
- and
- switching means responsive to the DC current from the controller means for selecting said high-pass filter means when said controller means does not output a DC current or selecting said bidirectional circuit means when said controller means outputs said DC current.
2 more elements
Dependencies are inferred from the claim text.