hmm thnx for tht, have read n searched a lot regardin dtmf n fsk encoding.... afaik, bsnl sends the caller id encoded using dtmf signal... but how its sent over the line, i mean the line voltages of the signals, and their duration etc. is wht i aint able to find... i'd also wanted to kno how the word is encoded, as in if any start bits or nething are transmitted. the whole project is to be implemented using a microcontroller/peripheral electronics. thts why i need these details.