Browse Prior Art Database

Tone Detector

IP.com Disclosure Number: IPCOM000089440D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Franklin, RE: AUTHOR

Abstract

This tone detector is accomplished by the illustrated detection logic that counts the time length of each cycle of the incoming tone frequency for four cycles.

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Tone Detector

This tone detector is accomplished by the illustrated detection logic that counts the time length of each cycle of the incoming tone frequency for four cycles.

A series of registers 11 each contain counts which differentiate between frequency ranges. Range counter 12 keeps selector 13 operated to gate the contents of the register 11, representing the next range, to down counter 14. Upon detection of the leading edge of the incoming signal the range counter is initially reset by controller 16 to the lowest count range. Signalled by controller 16, which receives the incoming tone frequency 10, the output of selector 13 is loaded into down counter 14. The counter then decrements until either the next leading edge is detected or the count reaches zero. If the count reaches zero, with a signal on line 17, controller 16 increments range counter 12 to select the next range. The output of the selector is again loaded into the down counter, which begins to decrement.

The process of selecting the next range, loading and decrementing the down counter 14, continues until the next leading edge of the signal is detected. When it is, the current value in the range counter 12 represents the frequency detected. This selected range count is used to select one of a plurality of possible ranges, the selected range being stored in register 19. Upon counter 15 counting 4 cycles of the signal in the same range, controller 16 causes register 20 to store the range selection...