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. 08, 1989
Filed:
Nov. 13, 1987
Walter A Halbig, Huntsville, AL (US);
ITEC, Inc., Huntsville, AL (US);
Abstract
A subscriber line interface circuit using integrated semiconductor circuit is provided with improved immunity to overvoltage and overcurrent conditions by increasing value of the battery feed resistors in series circuit with the ring and tip lines to increase the impedance encountered by a lightning-induced voltage spike to increase the survivability of the semiconductor circuit components. The battery supply voltage is increased to effect a commensurate increase in loop current, and the loop impedance is re-adjusted by appropriately configured operational amplifiers. A thermally responsive sensor is mounted in a heat-conducting relationship with resistive elements in the subscriber loop with an increase in temperature representing an overcurrent situation, such as power line cross-over, and provides a control signal effective to disconnect the subscriber loop from interface circuit.