When you are dialing a number, you are already making an outgoing call, now maybe you are telling me is limit, international call, domestic long distances?Ivanko said:Limit outgoing calls, all calls start with 0,9,or some other number : next, limit some call area 063,064 or some other : next, limit all calls except one
and some other functions and limiter is with PIC16F84 and MT8870.
you need to study about DTMF and you need to isolate the phone from the phone line. taking over the phone function, monitor the phone keypress by decoding the DTMF. if the key is correct, release the phone line and pass it to the phone.