The MX643 is a low power, low cost device that uses signal processing techniques to detect audible tone signals such as; Dial, Ring, Busy, Unobtainable, and other conditions found when placing a call throughout the world's telecom systems. The detection of these Call Progress stages is essential to the proper operation and application of automatic calling products. The MX643 offers identification of International Special Information Tones (SIT), reducing the time needed for cadence verification under Obtainable conditions. In addition to the SIT feature, single and dual tone decoding are added for better cross-system Call Progress monitoring. The MX643 offers these features in addition to the same performance levels and features of the MX633 Call Progress Tone Detector such as; detection and identification of U.S. Busy tones, thereby reducing the need to measure the tone cadence to identify U.S. Busy. The decoding and indicating of speech, or other Non-Call Progress signals, thus reducing voice-falsing of Call Progress tones and adding Voice-Answer as a connect prompt. Available in the industry standard 8-pin DIP, the MX643 is also available in a 16-pin SOIC making it pin compatible with the MX633DW (16-pin SOIC).