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. 23, 1987
Filed:
Dec. 07, 1984
Donald M Bellenger, Los Altos Hills, CA (US);
Buscom Systems, Inc., Santa Clara, CA (US);
Abstract
A single-tone receiver for a device which only needs simple data which can be encoded in the seven or eight single tones which can be generated by an ordinary pushbutton telephone is provided. A telephone line interface circuit receives a signal from the telephone line. The input signal is not filtered to separate the high-frequency tones from the low-frequency tones prior to their detection. A zero crossing detector coupled to the telephone line interface detects zero crossings of a received single-tone input signal. A microprocessor coupled to the zero crossing detector counts the number of zero crossings in a period and compares the count to counts corresponding to each of the seven single-tone frequencies.