Panasonic KX-F910BX Service Manual page 144

6. EXPLANATION OF ANALOG SECTION BLOCK DIAGRAM
(1)Function
The analog section serves as interface with the telephone line. The digital board (IC11) for transmission reception of FAX
signals, and the speech network IC (IC109) are connected to the NCU section. Switching between the digital board (IC11) and
the other sections is executed by means of a multiplexer in the NCU section. The control signals to the individual analog sections
are output mainly from the ASIC IC1, and the status information for the various sections also is held in the ASIC IC1.
Simple explanations for the various sections are given below.
2) Circuit Operation
[NCU Section]
Interface with the telephone line and external telephone. This is composed of bell detection circuit, pulse dial generation cir-
cuit, EXT.TAM OFF-HOOK detect circuit, vox circuit, amplifier circuit for line transmission and reception, sidetone circuit mul-
tiplexer circuit, etc. See below for details.
[Modem (IC11)]
This is used for FAX signal tone modulation, DTMF signal transmission, ring tone generation, and line transmission beep
generation. The DTMF signal and Beep are placed onto the TX system. The ring tone passes through the analog switch.
Output to the speaker via the power amplifier (IC241).
[Speech Network IC (IC109)]
This is special IC combining the hands-free and handset circuits in 1 chip. The handset and microphone are connected to
this circuit. At the time of hands-free operation, the SP output is outputted after passage through the power amplifier (IC241)
and the DTMF monitor tone and the pulse dial monitor tone output from IC11 (Digital Board) and IC151 (Analog Board) are
given as input to this IC and become the monitor tone at the time of handset dialing.
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