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:
Jan. 15, 1980
Filed:
Aug. 30, 1976
Akio Tanaka, Chicago, IL (US);
Zenith Radio Corporation, Glenview, IL (US);
Abstract
A two mode tuning system includes channel counters for determining system tuning by counting the LOF, a channel number comparator comparing the derived channel number with a desired channel number and PLL including a phase comparator for comparing equality pulses from the channel number comparator with a reference frequency. In the first mode the system tunes to a single frequency with the channel counters being operated continuously and the PLL tuning to the frequency corresponding to the selected channel number. In the second mode the system tunes to a frequency window with the channel counters being asynchronously sampled and an AFC circuit maintaining tuning within the window. Tuning cycle control means initiate the single frequency mode in response to a channel number input or an out-of-window tuning indication. The system switches to the tuning window mode after 200ms. Initially tuning to the 'center of the tuning window' relaxes the AFC requirements for a wide window system.