Panasonic KX-T7453, Service Manual, Page: 25 / 57

The voice serial data transmitted from PBX is sent to IC1 or IC2 by the serial data. The network
control, gain control , A/D conversion is performed in IC2, then the data is output from the handset
speaker. Q31 of the handset speaker performs the mute operation by controlling IC6.
3) Circuit diagram for transmission/reception signal path
Refer to page SCHEMATIC DIAGRAM ().
7.10. SP-PHONE CIRCUIT
1) Transmission signal path
The analog input signal from SP-phone microphone is input to the communication LSI through the IC2
built-in analog amplifier. In this LSI the network control based on A/D conversion and the handset
software and the gain control based on the down load data from the PBX are performed. The voice
data is sent to IC1 by the serial transmission. The voice data is transmitted between PBX and DPITS
with the protocol originated by KME. IC3 is the SP-phone amplifier, which turns ON/OFF using the
port of IC2. The analog switch of IC12 interrupts the input signal.
2) Reception siganl path
The voice serial data transmitted from PBX is sent to IC2 by the serial transmission. Then the signal is
output from the handset speakerphone after performing the network control, gain control, and A/D
conversion in IC2. The SP-phone microphone has the mute function, which interrupts the input signal
with the analog switch and controls the port of IC2 with Q26.
3) Circuit diagram for transmission/reception signal path
Refer to page SCHEMATIC DIAGRAM ().
8. TROUBLESHOOTING GUIDE
8.1. NO OPERATION.
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