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. 08, 1993
Filed:
Jun. 19, 1990
Andre Bonvallet, Asnieres, FR;
Robert Girard, Colombes, FR;
Daniel Perrein, Montigny Les Cormeilles, FR;
Alcatel Business Systems, Paris, FR;
Abstract
A low-frequency alternating current signal detector for recognizing tone signals in a central office line interface circuit connecting a private telephone installation to an analog telephone network subscriber line. The low-frequency alternating current signal detector includes an amplifier (1) connected to the input of a bandpass filter (2) and to the input of a first rectifier-filter (3), a second rectifier-filter (4) and a threshold presence detector (5) connected to the output of the bandpass filter (2). The output of the threshold presence detector (5) selectively enables comparison by a comparator (6) of the bandpass filter input and output signals and signalling of the presence of an alternating current signal.