Panasonic KX-T7565X Service Manual ▷ View online
8.5. RESET CIRCUIT
(1) CIRCUIT OPERATION
This circuit is used for transmission of a reset pulse to the CPU (IC2) at the following times, connecting the telephone line jack
and circuit operation.
and circuit operation.
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KX-T7565X / KX-T7565X-B
8.6. TONE GENERATION CIRCUIT
(1) FUNCTION
All system tones including COL, extension, busy, DTMF signal and key-in tones are sent from Pins 60 of IC2 and controls the
path by the Analog Switch (IC8).
path by the Analog Switch (IC8).
(2) CALLING TONES FROM COL AND EXT.
For a calling tone from a CO line or extension, the single row tone signal is output from Pin 60 of IC2 and the tone volume is
controlled by transistors Q999.
controlled by transistors Q999.
Ringer Volume Control
Level
OFF
LOW
HIGH
Q999
OFF
ON*
OFF
*CAUTION:
It is ON with ringer sound and it is OFF with no ringer sound regardless of the ringer volume.
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KX-T7565X / KX-T7565X-B
(3) BUSY STATION CALLING TONE
852 Hz and 697 Hz signals are output from Pin 61 of IC7 alternately at intervals of 60 ms.
The signal flow is shown below.
The signal flow is shown below.
(4) DTMF SIGNAL
A DTMF tone is generated by IC7 and the signal flow is shown below.
High Group
1209 Hz
1336Hz
1477Hz
697 Hz
1
2
3
Low
770 Hz
4
5
6
Group
852 Hz
7
8
9
941 Hz
*
0
#
(5) KEY-IN TONE
An 852 Hz single tone is used as the key-in tone. A tone is generated from IC7 and is heard at the speaker.
The signal flow is shown below.
The signal flow is shown below.
CONDITION
IC8 SWA
IC8 SWB
IC8 SWC
IC8 SWD
Ringing
OFF
OFF
OFF
ON
Call Waiting
OFF
OFF
ON
OFF
Tone Dial (Handset)
ON
ON
OFF
OFF
Tone Dial (Speakerphone)
ON
OFF
ON
OFF
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KX-T7565X / KX-T7565X-B
8.7. HANDSET CIRCUIT
(1) TRANSMISSION SIGNAL PATH
The analog input signal for the handset microphone is changed to a digital signal and sent through the telephone line via the
following path:
following path:
(2) RECEPTION SIGNAL PATH
The digital input signal from the telephone line is changed to an analog signal by IC3 and sent to the receiver via the following
path:
path:
(3) CIRCUIT DIAGRAM FOR TRANSMISSION / RECEPTION SIGNAL PATH.
8.8. SPEAKER-PHONE CIRCUIT
(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 hands-free mode.
unit is used in the hands-free mode.
(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.
This switching circuit is contained in IC8 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.
In other words, it can either transmit an outgoing signal or receive an incoming signal.
This switching circuit is contained in IC8 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.
(3) CONTROL SIGNAL PATH
Control signals for transmission and reception are input to IC8 via the following path:
(Transmission Control Signal Path)
(Reception Control Signal Path)
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KX-T7565X / KX-T7565X-B
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