The MX633 is a low cost, low power device that uses signal processing techniques to detect audible tone signals such as Dial, Ringing, Busy and other conditions found when placing a call throughout the world's telecom systems. Detection of these call progress stages is essential to the proper operation of automatic calling products. The MX633 adds new features to Call Progress monitoring. It detects and indicates the `U.S. Busy' tones, reducing the need to measure `tone cadence' to identify `U.S. Busy'. It also detects and indicates voice and other signals from Call Progress tones, reducing voice-falsing and adding voice-answer as a connection prompt. The MX633 may be used with a 3.0V to a 5.5V supply and is available in the following package styles: 8-pin PDIP (MX633P) and 16-pin SOIC (MX633DW).