interdigit interval

When pulse dialing is used, you need a certain amount of time free of "clicks" so the phone company knows that the digit is finished. When you are dialing on a rotary phone, you don't need to worry about this because the time it takes to turn the dial is sufficient. A modem that sends pulse codes must wait a specified amount of time before going from one digit to the next in a phone number. A value between 1/2 second a 1 second is usually used.