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:
Jun. 22, 1993
Filed:
Oct. 18, 1991
Hiroyuki Asano, Kawasaki, JP;
Fujitsu Limited, Kanagawa, JP;
Abstract
A telephone system comprises a multi-channel transmission apparatus for connecting a subscriber line to a telephone exchanger, where the transmission apparatus comprises: a subscriber interface for interfacing said subscriber line; a detecting circuit in the subscriber interface for detecting a change in a voltage on the subscriber line; and a discriminating circuit for discriminating whether the change detected by the detecting circuit is continuous or intermittent, upon discriminating the detected change in voltage as intermittent the discriminating circuit outputs a first alarm signal. The discriminating circuit may be formed of a software counter which counts a number of the intermittent signals for a predetermined period. The software counter does not require a bulky and expensive components, such as a 60 Hz filter. If the counted number is larger than a predetermined number the signal is determined to be intermittent. The first alarm signal may start a subscriber line tester which includes an AC voltage tester to measure an AC voltage on the subscriber line. If the measured AC voltage exceeds a predetermined criterion, it is determined that a power exposure has happened. This method allows a quick and correct detection of power exposure by merely adding a program into a currently provided micro processor, without requiring additional component.