Dennis Welbourn,
thanks for your reply, i have gone through chips like MT8870 for DTMF decoding etc...but i was looking for some thing which can save the cost of this chip...

Any ways... lets suppose if iam using Pulse Dialing Telephone Sets then if i store two numbers in the controller e.g.

10 in register R1
20 in register R2

when ever the user of telephone no.20 pick up the telephone set and dial "10" then the controller count the incoming make and break ratio which is 60:40 and compare the incoming pulses with the stored number and if the stored number is equal to the dialed number then controller sents a ring back tone to the user and also sents a signal to 60 volts Ac Supply so that ring can occur on telephone having number "10"

Is there any component which i should connect in order to make controller count the incoming pulses .... i know that using timer as pulse counter and using i think pin3.2 will do the job but what will happen in case of 8 or 16 telephone users....where to connect there wires from the SLIC or Phone Line Circuit.