You could use a Timer that is set for a little longer than the span between pulses. Each pulse resets the timer and increments the counter. When the Timer times out, lock in your Counter as your number value and turn off the Timer. Loop waiting for a next incoming pulse, restart the Timer and start again. Have a second variable that increments with each saved value. If you normally use 7 digits (that would be a local call in the US), initiate the call after 7 number entries. You could also use a second timer that automatically dials when increments of 7 or 10 digits have been entered and the second Timer expires. As for the initiation of the dialing, I know there is a way to use TONEs to create dual tones (modern method of creating a number), but I don't know enough about telephone systems to know much more.