The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 14, 2001
Filed:
Mar. 25, 1998
Jeffrey Haskell Derby, Chapel Hill, NC (US);
David Ross Thomas, Apex, NC (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
A network interface circuit includes an off-hook/on-hook circuit, responsive to the communications network, that provides an off-hook voltage substantially equal to the communications network voltage in an off-hook state and that provides an on-hook voltage in an on-hook state. A voltage controlled current source provides a load current which is proportional to a communications network voltage provided by the communications network. A divider circuit, responsive to the off-hook/on-hook circuit, provides an input voltage and produces an over-voltage, wherein the input voltage is proportional to off-hook or on-hook voltage. A clamping circuit limits the input voltage to one of a first or second predetermined value based on the operating mode and generates a current limited voltage. A control circuit, responsive to the over-voltage and the current-limited voltage and the operating mode and responsive to the off-hook/on-hook circuit, sets the network interface circuit in the off-hook state or the on-hook state based on the input voltage, the current-limited voltage, and the operating mode. Related methods and apparatus are also discussed.