Hi
This is shankar
with this i have attached a circuit that controls the switching of electrical appliances using dtmf(double tune multi frequency) signals as control signals.
please help me by giving ur suggestion about how the ckt works
It looks to me like the 555 is wired as a comparator, the electrolytic capacitor on the feed from the opto-isolator suggests to me that it won't pass any DTMF frequencies, and is more likely to be simply passing the ringing pulses. Everything else in done in software, presumably counting the number of rings to turn the selected relay on?.