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:
Oct. 05, 1993
Filed:
Jul. 15, 1991
Andrew S Crowe, San Jose, CA (US);
Tain-Shiuann Lin, San Jose, CA (US);
Rolm Company, Santa Clara, CA (US);
Abstract
To detect tones for call progress monitoring, hysteresis apparatus is provided whereby the output of a typical tone detector such as a comparator operating in conjunction with a selective filter is monitored by a counter. The counter is incremented and decremented according to whether the input is indicative of the presence or absence of a tone. If the counter reaches a predetermined count within a given period of time, then an indication is made that the tone exists. If the counter does not reach this predetermined count or threshold within the applicable time, then it is an indication that the tone does not exist. The thresholds of the counters plus the amount by which a counter may be incremented or decremented for each input signal is variable for each tone. In this manner a plurality of different tones on a common communications channel such as a telephone line can be continuously monitored even though each tone may be very close in frequency and the particular communications channel being monitored may be subjected to various types of noise.