How i can generate these tones from the controller and make controller to suply tones to all sets in case all telephone sets goes off-hook.. I know i have to make a delay of 400Hz for Dial Tone , for ring back tone same delay but with 0.5 seconds off and 0.5 On condition , for busy tone same but with 0.1 Second On and 0.1 Off... for this there are call progress geneartion IC like M-991 but that are not avaiable in my region... any suggestions..
" ... delay of 400Hz ... " You mean a frequency of 400Hz. Why not just use a timer to generate the frequency, and then gate it on & off to give the required cadence?
ya i know that ysing 555 will do the job but i want to do this using controller..
"Timer" could equally well mean one of the 8051's timers. That's what I was thinking of.