Panasonic KX-T7735RU / KX-T7735RUPP Service Manual ▷ View online
8.4. TONE GENERATION CIRCUIT
Function:
This circuit generates all system tones including COL, extension, busy, DTMF signals and key in confirmation tones during the
power failure mode and is comprised of IC1(DTMF Generator) and IC5 (Analog Switch).
This circuit generates all system tones including COL, extension, busy, DTMF signals and key in confirmation tones during the
power failure mode and is comprised of IC1(DTMF Generator) and IC5 (Analog Switch).
Circuit Operation:
For an output of a single row tone, the row terminal and the each column terminals intersecting with it are required to be brought
a low state. For a dual tone output, one row terminal and one column terminal are brought to low state.
For an output of a single row tone, the row terminal and the each column terminals intersecting with it are required to be brought
a low state. For a dual tone output, one row terminal and one column terminal are brought to low state.
CONDITION
IC1 pin52
IC5 SWA
IC1 pin53
IC5 SWB
IC1 pin54
IC5 SWC
IC1 pin55
IC5 SWD
Ringing
L
OFF
L
OFF
L
OFF
H
ON
Call Waiting
L
OFF
L
OFF
H
ON
L
OFF
Tone Dial (Handset)
H
ON
H
ON
L
OFF
L
OFF
Tone Dial (Speakerphone)
H
ON
L
OFF
H
ON
L
OFF
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8.5. HANDSET CIRCUIT
1) Transmission Signal Path
The input signal for the handset microphone is sent through the telephone line via the following path:
Handset MIC(JK2)
The input signal for the handset microphone is sent through the telephone line via the following path:
Handset MIC(JK2)
→ JK3 → C24 → R26 → C34 → Q5 → C21 → R21 → Q3 → C4 → T1 → C3 → Q1 → D1 → Telephone Line
2) Reception Signal Path
The input signal from the telephone line is sent to the receiver through the following path:
Telephone Line
The input signal from the telephone line is sent to the receiver through the following path:
Telephone Line
→ D1 → Q1 → C3 → T1 → C4 → Q3 → R10 → C8 → R12 → Q4 → C26 → R32 → IC10 → C32 → R34 → C27
→ R208 → Q8 → C31 → JK3 → JK2 → Handset Speaker
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8.6. SPEAKERPHONE CIRCUIT
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 hands-free mode.
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 hands-free mode.
Circuit Operation:
The speakerphone can only provide a one-way communication path 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.
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 IC3 and consists of a Voice Detector, Tx Attenuator, Rx Attenuator, Comparator and Attenuator
Control. The circuit analyzes whether the Tx (transmit) or Rx (receive) signal is louder, and then it processes the signals so 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 Rx signal, and supplies DC input to the Attenuator Control corresponding to the Rx signal.
The Attenuator Control provides a control signal to the Tx and Rx Attenuator to switch the appropriate signals ON and OFF.
The Attenuator Control also detects the level of the volume control to automatically adjust the volume for changing ambient
conditions.
The speakerphone can only provide a one-way communication path 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.
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 IC3 and consists of a Voice Detector, Tx Attenuator, Rx Attenuator, Comparator and Attenuator
Control. The circuit analyzes whether the Tx (transmit) or Rx (receive) signal is louder, and then it processes the signals so 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 Rx signal, and supplies DC input to the Attenuator Control corresponding to the Rx signal.
The Attenuator Control provides a control signal to the Tx and Rx Attenuator to switch the appropriate signals ON and OFF.
The Attenuator Control also detects the level of the volume control to automatically adjust the volume for changing ambient
conditions.
1) Control Signal Path
Control signal for transmission and reception are input to IC3 via the following path:
(Transmission Control Signal Path)
MIC(CN2)
Control signal for transmission and reception are input to IC3 via the following path:
(Transmission Control Signal Path)
MIC(CN2)
→ IC3 Pin 9 → IC3 Pin 10 → IC3 Pin 3 → IC3 Pin 4 → IC3 Pin 5
(Reception Control Signal Path)
Telephone Line
Telephone Line
→ Q3 → Q4 → IC3 Pin 7
2) Transmission/Reception Switching
The comparison result between Tx and Rx output is a DC level at IC3 Pin 26.
Tx level is high .................... Pin 21-Pin 26=6mV
Rx level is high .................... Pin 21-Pin 26=150mV
The comparator output is connected to the attenuator control inside IC3.
The comparison result between Tx and Rx output is a DC level at IC3 Pin 26.
Tx level is high .................... Pin 21-Pin 26=6mV
Rx level is high .................... Pin 21-Pin 26=150mV
The comparator output is connected to the attenuator control inside IC3.
3) Voice Detector
The output of the mic amp (Pin 10 of IC3) is supplied to Pin 14 of IC3 as a control signal for the voice detector.
The output of the mic amp (Pin 10 of IC3) is supplied to Pin 14 of IC3 as a control signal for the voice detector.
4) Attenuator Control
The attenuator control detects the setting of the volume control through Pin 25 of IC3 and automatically adjusts the volume for
changing ambient conditions.
The attenuator control detects the setting of the volume control through Pin 25 of IC3 and automatically adjusts the volume for
changing ambient conditions.
5) Transmission Signal Path
The input signal from the microphone is sent through the circuit via the following path:
MIC(CN2)
The input signal from the microphone is sent through the circuit via the following path:
MIC(CN2)
→ C64 → R206 → C59 → IC3 Pin 9 → IC3 Pin 10 → R45 → C48 → IC3 Pin 3 → IC3 Pin 4 → C41 → R41 → Q3 →
C4
→ T1 → C3 → Q1 → D1 → JK1 → Telephone Line
6) Reception Signal Path
Signals received from the telephone line are output to the speaker via the following path:
Telephone Line
Signals received from the telephone line are output to the speaker via the following path:
Telephone Line
→ D1 → Q1 → C3 → T1 → C4 → Q3 → R10 → C8 → R12 → Q4 → C42 → R42 → C46 → IC3 Pin 29 → IC3
Pin 28
→ R57 → C62 → C61 → IC3 Pin 20 → IC3 Pin 16 → C63 → CN3 Speaker
7) Busy Tone Detector Circuit
The busy tone detection for automatic redealing is executed as follows.
Telephone Line
The busy tone detection for automatic redealing is executed as follows.
Telephone Line
→ D1 → Q1 → C3 → T1 → C91 → R91 → IC6 → D3 → R99 → Q20 → IC1 Pin 64
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