Coded data generation or conversion – Code generator or transmitter
Patent
1992-08-18
1995-03-14
Horabik, Michael
Coded data generation or conversion
Code generator or transmitter
379362, 327115, 327113, 375272, 375275, 375306, H04Q 100
Patent
active
053980310
ABSTRACT:
A DTMF signal generating circuit for producing output of a selection signal having a frequency corresponding to a signal entered from push buttons. A high frequency oscillation signal output from an oscillatory circuit are delivered to both a first frequency dividing circuit for dividing high frequency signals by a first dividing ratio and a second frequency dividing circuit for dividing high frequency signals by a second dividing ratio, thereby producing two kinds of divided signals each of which has its own predetermined frequency. A fractional frequency division is then accomplished by switching from an output of a first frequency dividing circuit to an output of a second frequency dividing circuit at a predetermined timing. The signals output form the switch are then counted by a ROM address counter, producing an output of an address value signal. The address value signal is then delivered to a sine wave output ROM in which peak values in response to a predetermined sine waveform are preliminary stored in the order of address value, so that 32 digital data corresponding to the input address values are output. Concurrently, a switching rate generator of a frequency dividing circuit supplies a switching timing signal, which is determined by both an address value signal delivered from the ROM address counter and a dividing ratio signal entered from the key input control circuit, to a key input control circuit, thereby generating DTMF signals highly similar to the standard DTMF frequency.
REFERENCES:
patent: 4748640 (1988-05-01), Staley
patent: 4922527 (1990-05-01), Nonami
patent: 4998276 (1991-03-01), Hasegawa
Horabik Michael
Rohm & Co., Ltd.
Zimmerman Brian
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