Holtek ht9200 dtmf generator holtek ht9200b dtmf generator 25v to 55v supply voltage 2ua standby current 015vrms dtmf ac level 358mhz system frequency 950ua operating current 01ma output drive current 68k pull high resistance 20 to 75c 14 sop case the ht9200ab tone generators are designed for mcu interfaces they can be instructed by a mcu to generate 16 dual tones and 8 single tones from the dtmf pin the ht9200a provides a serial mode whereas the ht9200b contains a selec