The ZLS38503 voice-processing firmware supports a range of features, including voice recording and prompting, dual-tone multifrequency (DTMF) receiver, tone generator, call-progress tone detection, and caller ID. The functions work with the ZL38004 hardware platform and ZLS38502 advanced speakerphone firmware to provide a complete solution.

Voice prompting asks the user what function he/she would like to perform. The signaling block includes caller ID type 1 detection, DTMF detection, tone generator (including DTMF generation), and call-progress tone detection.