The M-984-02 Special Information Tone Detector is a monolithic integrated circuit designed to provide reliable detection of many common telephone network status signals. In particular, it detects the signals known as Special Information Tones (SITs) or error tones as defined by the CCITT, and single tones often used as dial tone, audible ringing, and other general progress indications. The M-984-02 uses CMOS switched capacitor filters and a crystal time base to achieve the high stability and accuracy specified. Each tone detection window has an associated output pin, which can be placed in a high impedance state for use with time-share microcomputer bus applications.