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:
Jun. 19, 1990
Alcatel Business Systems, Paris, FR;
Abstract
Detector for telephone charging signalling in the form of periodic pulses derived from alternating current signals at specific frequencies transmitted in analog form by means of a line (2) comprising two wires (A, B), for example to a central office line interface circuit of a private telephone installation connected to an analog network subscriber line. The detector comprises an input filter (4) centered on the frequency (Ft) of the expected signalling, a sample and hold circuit (6) connected to the output of the input filter (4) and to the output of a clock (7) supplying a signal (HE) whose frequency (FE) is close to the value (Ft), a lowpass filter (8) within the band of which the characteristic signal from the sample and hold circuit is included, and a level detector (9) adapted to supply a presence signal for a characteristic signal at a level above a predetermined threshold at the output of the lowpass filter (8).