Circuit for generating dual-tone multi-frequency signals and hig

Details Circuit for generating dual-tone multi-frequency signals and hig Circuit for generating dual-tone multi-frequency signals and hig

1989-03-02

1990-07-03

Heyman, John S.

Telephonic communications

Special services

Anonymous party

379361, 34082548, 377 56, H04M 150, H04M 174, H03K 492, H03L 716

Patent

active

049394703

ABSTRACT:
A circuit for generating dual-tone multi-frequency (DTMF) signals and high/low-tone signals from digital data with designating frequencies of high-tone or high-frequency group and frequencies of low-tone or low-frequency group, and at least one digital control signal. The circuit includes a signal controlling logic circuit for decoding the digital data in response to the digital control signal, a circuit for generating a fixed clock pulse, a frequency dividing circuit of low-frequency group for generating first clock pulses, a frequency dividing circuit of high-frequency group for generating second clock pulses, first clock device for generating a plurality of pulses having a duty cycle of 50% by dividing the first clock pulses, second clock device for generating a plurality of pulses having a duty cycle of 50% by dividing the second clock pulses, and a signal synthesizing circuit for synthesizing the dual-tone multi-frequency signals or high/low-tone signals of analog sine-wave deprived of higher-harmonic wave component by inputting the clock pulses of the odd frequency.

REFERENCES:
patent: 3787836 (1974-01-01), Hagelbarger
patent: 3820028 (1974-06-01), Thomas
patent: 4132871 (1979-01-01), Lake
patent: 4390754 (1983-06-01), Holberg
patent: 4558282 (1985-12-01), Lowenschuss
patent: 4727570 (1988-02-01), Tarbouriech
patent: 4746870 (1988-05-01), Underhill

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