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| IT- A4000
Dial : Tone Dial
Pulse output
of dialer IC maintains
High and Q301
remains
ON in tone type. If you press the dial key of the
phone when
the power
supply is cut off, the tone signal is output from dialer IC (DTMF)
output, input in the
speech
network
MF
input
and
transmitted
to the circuit.
D922
is the protective
diode
to prevent
inputting
the irregular voltage
to IC902.
When the telephone is connected to a commercial use power supply:
Dial : Pulse Dial
When
you lift up the handset, you will hear the dial tone. If you press the dial keys of the phone
S807, S808,
$809, $813, $814, S815, S819, $820, S821, S825, S826 and S827 when the power
supply is on, DP output signal of
ASIC
IC (IC802)
outputs
High, Low
corresponding
to the dial signal.
Dial : Tone Dial
DP output signal of ASIC
IC maintains
Low
and Q301 remains
ON in tone type. DTMF
signal is generated
by
converting the digital signal from ASIC into the analog signal with CODEC
IC (IC804). This signal is input into
the speech network MF input.
.
2-5. Dial : Speaker Phone Call
When
you press the speaker phone button, you will hear the dial tone. The same
dial operation
of the handset
call when
both the pulse dial and the tone dial are connected
to a commercial
use power
supply, is conducted.
2-6. Hold
When
you press the Hold button, IC806 and Hold output (12pin) becomes
High, makes
Q401, Q403 and Q420 ON,
sets receiving and sending into Mute.
2-7. Answering Machine
2-7-1. Response message (OGM) recording
The signal from the microphone
is converted into the digital signal by CODEC
IC (IC803)
after being amplifie
by IC501, and goes to ASIC IC (IC802).
ACIC IC informs DSP.IC (C801)
of this signal and returns the signal to ASIC after signal compressing procedure
in DSP.
This signal is recorded
in DRAM.
2-7-2. Ringer signal detection and circuit transmission of the response message (OGM)
When
you press the ANSWER
button
to set the answering machine, the button will light up. When
the ringer
signal is input from the circuit, the ringer signal reaches ringer IC and IC280 via S301 (1/2), RY301, LF301, R280
and C280 to make the speaker ring.
At the same
time, photocoupler PH280
is driven. DSP IC (IC801) detects this output through buffer IC
(IC805)
ASIC
IC (IC802). Relay RY301
and the circuit is closed after ringing for a fixed time.
When
the fixed record OGM
is recorded, DSP receives the data recorded in DRAM
through ASIC IC, the data
procedure
is conducted, and
returns
to ASIC.
The digital data from
ASIC
is converted
into the analog signal by CODEC
IC (IC804).
The analog signal converted
by CODEC
is amplified, input to the speech network
IC, MF
input, and transmitted
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