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:
Mar. 07, 1989
Filed:
Aug. 03, 1987
Yoshiki Sano, Tokyo, JP;
Masaaki Tsukada, Tokyo, JP;
Tamura Electric Works, Ltd., Tokyo, JP;
Abstract
A called party response detecting apparatus includes a plurality of filter units for respectively detecting natural frequency components included in a plurality of signals sent from a telephone line. The apparatus also includes switching units for switching input levels of the filter units in a plurality of steps and a continuous signal detector for detecting that a logical sum output from the filter units has continued for a predetermined interval of time. An input level control unit operates to control the switching units to set an input level at a lowest level while waiting for a signal and also to reset the input level at a predetermined level different from the lowest level when an output is obtained from one of the filter units. During this reset operation, the input level control unit decreases the input level in steps until an output is obtained from the continuous signal detector. The apparatus further includes a discriminator for determining, when the continuous signal detector continuously detects logical sum outputs from the filter units for the predetermined time, a plurality of signal tones and a called party response in accordance with the frequency pattern of the outputs from the filter units within the predetermined time.