Automatic Ringback Detector
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
This invention relates to a method and apparatus for extracting a signal out of noise and ascertaining its type. More particularly, the invention relates to a method for concurrently detecting a signal envelope and counting a predetermined number of zero access crossings in order to conclude that a signal is present. Discrimination among signal types may be executed by any one of a number of conventional means. The application for the method and apparatus is in the environment of automatic ringback signal detection for an automatic dialing system. This ringback signal is detected when the circuit is enabled after an automatic dial operation. Other signals which may occur at that time, such as a busy signal, noise, voice, or dial tone, are accurately rejected.