ZL49031

The ZL49031 is a family of high performance DTMF receivers which decode all 16 tone pairs into a 4-bit inary code. The ZL49031 incorporate an AGC for wide dynamic range and are suitable for end-to-end signalling. The ZL49031 provides an early steering (ESt) logic output to indicate the detection of a DTMF signal and requires external software guard time to validate the DTMF digit. The ZL49031, with preset internal guard times, uses a delay steering (DStD) logic output to indicate the detection of a valid DTMF digit. The 4-bit DTMF binary digit can be clocked out synchronously at the serial data (SD) output. The SD pin is multiplexed with call progress detector output. In the presence of supervisory tones, the call progress detector circuit indicates the cadence (i.e., envelope) of the tone burst. The cadence information can then be processed by an external microcontroller to identify