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:
May. 20, 2003
Filed:
Feb. 17, 1999
Timothy F. Murphy, Ramona, CA (US);
Christopher R. Hansen, Grass Valley, CA (US);
3Com Corp., Santa Clara, CA (US);
Abstract
A method and apparatus for the detection of one or more telephone off-hook conditions using an analog-to-digital converter to detect voltage changes between tip and ring lines of a telephone network loop. An isolation network provides substantial electrical isolation for a detection device from voltage surges on the tip and ring lines of a “plain old telephone system” (POTS) network. The isolation network also provides a minimal load on the POTS wiring system, so as not to cause a false detection of an off-hook condition by central office equipment. A gain amplifier is used to scale the tip and ring voltage to a suitable range for an analog-to-digital converter (ADC). The ADC outputs a digital voltage value to a decision-making element, such as a microprocessor, a digital signal processor, or a state machine. The decision-making element can detect when multiple POTS devices coupled to the network wiring loop go into an off-hook state. The invention can also detect and compensate for a tip/ring wiring pair reversal and is highly reliable.