you can detect the pulses by using modem ; i think that! i am just in second year of diploma engg. so i doesn't no that it is right or wrong. but i want to suugest you . you can calculate the bill using computer by giving him the information about the billing in detail , i.e. area code of caller & receiver both , in 1 call how many pulses are permitted by the telecom company & the time spend in that call. please forgive me if i am wrong. thanking you. yours friendly vineet vijay gajendragadkar