Analog Circuit - Panasonic KX-T7665AL Service Manual

10.8. ANALOG CIRCUIT

This circuit performs the setting of the call path/vol. adjustment in each call mode by IC4.
The audio gain of each call is determined by download data from PBX.
· IC2 sends each audio data to IC3 by PCM interface.
· IC2 receives each audio data from IC3 by PCM interface.
1. Handset Call
Transmitting signal is inputted from handset microphone and amplified by IC4 built-in Amp → A/D conversion →Gain
adjustment by IC4 →inputted to IC3 and IC2 in PCM data →then sent to PBX.
Receiving signal is inputted from PBX →IC2→IC3→D/A conversion after the input to IC4 in PCM data→Gain adjustment by
DSP of IC4→Pin 26 of IC4→ outputted from Q51 to handset.
2. Speakerphone Call
The speakerphone mode can only provide a one-way communication path.
IC3 compares transmitting signal and receiving signal during speakerphone mode, then provide a one-way communication
path.
Transmitting signal is inputted from SP phone mic. and amplified by IC4 built-in Amp→ A/D conversion→inputted to IC3 in
PCM data→Gain adjustment by IC3→inputted to IC2→ then sent to PBX.
Receiving signal is inputted from PBX is →IC2→Gain adjustment by IC3 →inputted to IC4 in PCM data→D/A
conversion→pin 24 of IC4→pin 27 of IC4→pin 28 of IC4→pin 29 of IC4→ outputted from pin 3 and 4 of IC4 to speaker.
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KX-T7665AL / KX-T7665X