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:
Feb. 26, 1985
Filed:
Aug. 30, 1982
Roger F Atkinson, Huntsville, AL (US);
Itec, Inc., Huntsville, AL (US);
Abstract
An inexpensive universal telephone signalling tone receiver employs switched capacitor filters to provide selective tone reception in accordance with pre-selected clock signal frequencies. The clock signals, which in the preferred embodiment are provided from an EPROM, are employed to determine the pass band center frequency for respective filters. The selected signalling tones, when received, are rectified and passed to respective sample and hold circuits, the output signals of which are sequentially applied for processing to a common analog-to-digital converter through a multiplexer. Depending upon the clock pulse frequencies programmed for a particular application, the receiver can be used for various signalling protocols, including R1 and R2, in either direction, as well as other single or multi-tone signalling applications. In multifrequency signalling applications, the receiver selectivity permits the processing circuitry to look for two tones of significant amplitude among noise components rather than to continuously adjust threshold detectors, in response to the wide band signal level.