11KX-TG9341T/KX-TG9342T/KX-TG9343S/KX-TG9343T/KX-TG9344T/KX-TGA931S/KX-TGA931T4.4. Circuit Operation (Base Unit)General Description:(DSP, Flash Memory) is a digital speech/signal processing system that implements all the functions of speech compression,record and playback, and memory management required in a digital telephone answering machine.The DSP system is fully controlled by a host processor DSP. The host processor provides activation and control of all that func-tions as follows.4.4.1. DSP (Digital Speech/Signal Processing: IC501)• Voice Message Recording/Play backThe DSP system uses a proprietary speech compression technique to record and store voice message in Flash Memory.An error correction algorithm is used to enable playback of these messages from the Flash Memory.• DTMF GeneratorWhen the DTMF data from the handset is received, the DTMF signal is output.• Synthesized Voice (Pre-recorded message)The DSP implements synthesized Voice, utilizing the built in speech detector and a Flash Memory, which stored the vocabulary.• Caller ID demodulationThe DSP implements monitor and demodulate the FSK/DTMF signals that provide CID information from the Central Office.• Digital SwitchingThe voice signal from telephone line is transmitted to the handset or the voice signal from the handset is transmitted to the Tele-phone line, etc. They are determined by the signal path route operation of voice signal.• Block Interface CircuitRF part, LED, Key scan, Speaker, Microphone, Telephone line.4.4.2. Flash Memory (IC601)Following information data is stored.• Voice signalex: Pre-recorded Greeting message, Incoming message• Settingsex: message numbers, ID code, Flash Time, Tone/Pulse