Matsushita Electric KX-TSC35MXW, Service Manual

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following path: Tel line R1/C1 D1 Pin 1 of IC1 Pin 8 of IC1 C6 T1 C625
Speaker
9.2. Line Interface
In talk status, SW101 become ON and Q103 base changes to high level, causing Q103, Q101 to
turn on and resulting in a line loop.The loop current flows from D101(+) Q101 Q108
R124 D106 in that order, A pulse signal that repeated switches between high and low logic is
output from pin 39 of the CPU.This switches the line loop on and off, generating the dial pulse
signal.
9.3. MODULE BLOCK DIAGRAM
9.3.1. Speakerphone Circuit
9.3.1.1. Function
The circuit controls the automatic switching of the transmitted and received signals, to and
from the telephone line, when the unit is used in the hands -free mode.
9.3.1.2. Circuit Operation
The speakerphone can only provide a one-way communication path.
In other words, it can either transmit an outgoing signal or receive an incoming signal at a given
time, but cannot do both simultaneously. Therefore, a switching circuit is necessary to control
the flow of the outgoing and incoming signals.
This switching circuit is contained in IC601 and consists of a Voice Detector, TX Attenuator, RX
Attenuator, Comparator and Attenuator Control. The circuit analyzes whether the TX(transmit)
or the RX(receive) signal is louder, and then it processed the signals such that the louder signal
is given precedence.
The Voice Detector provides a DC input to the Attenuator Control corresponding to the TX
signal.
The Comparator receives a TX and a RX signal, and supplies a DC input to the Attenuator
Control corresponding to the RX signal.
The Attenuator Control provides a control signal to the TX and the RX attenuator to switch the
appropriate signals on and off. The Attenuator Control also detects the level of the volume
control to automatically adjust for changing ambient conditions.
1. Transmission signal path:
The input signal from the microphone is sent through the circuit
via the following path:MIC Pin 9 of IC601 Pin 10 of IC601
Pin 3 of IC601 Pin 4 of IC601 R601 C602 Q108 Tel line.
2. Reception signal path:
Signals receive from the telephone line are outputted at the
speaker via the following path:Tel line Q108 Q109 C112
R600 C603 Pin 27 of IC601 Pin 26 of IC601 Pin 19 of
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