Dual tone multiple frequency generator

摘要: A dual-tone multiple frequency signal generator is provided for use with telecommunications systems, data transfer systems and other applications. The tone encoding system utilizes MOS/LSI integrated circuitry on a single chip powered directly by telephone line voltages. An electronic keyboard circuit provides synchronized pulses to decode single-pole, single-throw switches row column. crystal-controlled oscillator generates reference which divided according the column of an activated switch obtain two pulse signals having frequencies representative switch. outputs divider are fed programmed logic array digitally coded each representing sinusoidal waveform. digital-to-analog ladder network converts continuous sine waves, operational amplifier combines waveforms provide output. also common functions transmission, including applying power oscillator, disconnecting audio transmitter attenuating input receiver. Complementary-symmetry, metal-oxide semi-conductor elements implement design bi-polar transistors same performing some function switching.