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(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.
(4) DTMF SIGNAL
A DTMF tone is generated by IC7 and the signal flow is shown below.
697 Hz
770 Hz
Low
Group
852 Hz
941 Hz
(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.
CONDITION
Ringing
Call Waiting
Tone Dial (Handset)
Tone Dial
(Speakerphone)
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:
High Group
1209 Hz
1336Hz
1
4
7
*
IC8 SWA
IC8 SWB
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
20
1477Hz
2
3
5
6
8
9
0
#
IC8 SWC
IC8 SWD
OFF
ON
ON
OFF
OFF
OFF
ON
OFF
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