Panasonic KX-T7630 Service Manual page 21

PCM data
Transmitting signal inputted from headset microphone is
controlled by transmission switching SW IC7 as below.
IC3-pin 52 H : Headset Call
(IC3-pin 52 L : Handset Call)
Receiving signal inputted from PBX is
of IC5 D/A conversion after the input to IC4 in PCM data
built-in Amp output
headset.
3. Speakerphone Call
Speakerphone call realizes all double-call by DSP(echo canceller)
built in IC5. For a call in the most appropriate condition, DSP
checks voice level of the calling party, acousticity in a room, voice
level of the other party and state of the line of contact, and cancels
echo in transmitting and receiving at the start of calling. It
operates in a half double-call state in a few seconds for the check.
Transmitting signal is inputted from SP phone mic. and amplified
by IC4 built-in Amp
data Gain adjustment by DSP of IC5, then sent to PBX through
echo canceller.
Receiving signal inputted from PBX is
through echo canceller of IC5
conversion
to speaker.
Power Amp IC2 is controlled as follows;
IC3-pin 51 L
IC3-pin 51 H
11. IC DATA
11.1. IC5 (ASIC)
Gain adjustment by DSP of IC5
outputted from Q16(transistor for buffer) to
A/D conversion
IC4 built-in Amp output
IC2-ON
IC2-OFF
Gain adjustment by DSP
inputted to IC5 in PCM
Gain adjustment by DSP
inputted to IC4 in PCM data
outputted from IC2(Amp)
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then sent to PBX.
IC4
D/A