Panasonic KX-TC1025RUB Service Manual ▷ View online
26.8. Power Supply Circuit
Function:
Power from the AC adaptor passes through and is provided to a system voltage.
Power from the AC adaptor passes through and is provided to a system voltage.
Circuit Operation:
Power from the AC adaptor is supplied directly to the charge circuit its voltage. Its voltage is regulated in IC801 and IC301. The
IC801 voltage at pointe
Power from the AC adaptor is supplied directly to the charge circuit its voltage. Its voltage is regulated in IC801 and IC301. The
IC801 voltage at pointe
is regulated to 5.5 V. The IC301 voltage at pointe
is regulated to 5.0 V.
26.9. CPU Operation
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26.10.1. Function:
This circuit controls the automatic switching of the transmitted
and received signals, to and from the telephone line, when the
unit is used in the Speakerphone (hands-free) mode.
and received signals, to and from the telephone line, when the
unit is used in the Speakerphone (hands-free) mode.
26.10.2. 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
processes 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.
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
processes 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.
26.10.2.1. Transmission signal path
The input signal from the microphone is sent through the circuit
via the following path:
Mic
via the following path:
Mic
→
Pin 9 of IC601
→
Pin 10 of IC601
→
Pin 3 of IC601
→
Pin 4 of IC601
→
R637
→
Pin 17 of IC301
→
Pin 18 of IC301
→
Telephone Line.
26.10.2.2. Reception signal path
Signals receive from the telephone line are outputted at the
speaker via the following path:
Telephone Line
speaker via the following path:
Telephone Line
→
Pin 25 of IC301
→
Pin 24 of IC301
→
Q602
→
Pin 29 of IC601
→
Pin 28 of IC601
→
Pin 20 of IC601
→
Pin
16 of IC601
→
Speaker.
26.10.2.3. Control signal path:
Control signals for transmission and reception are inputted to
IC601 via the following path:
(Transmission Control Signal Path)
Mic
IC601 via the following path:
(Transmission Control Signal Path)
Mic
→
Pin 9 of IC601
→
Pin 10 of IC601
→
R601
→
C604
→
Pin 3 of IC601
→
Pin 4 of IC601
→
C607
→
R603
→
Pin 5 of
IC601.
(Reception Control Signal Path)
Telephone Line
(Reception Control Signal Path)
Telephone Line
→
IC301
→
Q602
→
C606
→
R602
→
Pin 7 of
IC601.
26.10.2.4. Transmission/reception
switching
The comparison result between Tx and Rx outputs as a DC
level of IC201 of Pin 26.
Tx level is high ........ Pin 26 = Pin 21 — 6 mV
Rx level is high ........ Pin 26 = Pin 21 — 150 mV
level of IC201 of Pin 26.
Tx level is high ........ Pin 26 = Pin 21 — 6 mV
Rx level is high ........ Pin 26 = Pin 21 — 150 mV
26.10.2.5. Voice detector
The output of the mic amp (Pin 10 of IC601) is supplied to Pin
14 of IC601 as a control signal for the voice detector.
14 of IC601 as a control signal for the voice detector.
26.10. Speakerphone Circuit
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