1. PCD3311 DTMF Modem Musical-Tone Generators|
The PCD3311C and PCD3312C are single-chip silicon gate CMOS integrated circuits. They are intended principally for use in telephone sets to provide the dual-tone multi-frequency (DTMF) combinations required for tone dialling systems. The various audio output frequencies are generated from an on-chip 3.58 MHz quartz crystal-controlled oscillator. A separate crystal is used, and a separate microcontroller is required to control the devices. 28 pages.