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IT- A4000
|
SECTION 2
DESCRIPTION
2-1. Ringer
Connect
modular
jack MJ301
to the circuit. Circuit
Ll and L2 are rectified
at D302
via LF301, R280
and
C280
through
hook
switch
S301
(1/2) and relay RY301. The voltage
of the rectified call signal is input to ringer IC
(IC280), and
the ringer tone
is generated
at the speaker.
D107
is the protective
diode
to prevent
inputting
irregular
voltage
to IC280. SG301
protects
the circuit
from
inputting irregular voltage
as the surge
voltage.
2-2. Call : Handset
When you lift up the handset, S301 (1/2) and S302 (2/2) will operate. The voltage is input to D301 through S301
(1/2), and will rectify and reach R303 and Q301.
R303 is connected
to the base of Q302 and sets it to HIGH.
Q301 becomes
ON and the circuit voltage reaches speech network IC301. The speech network
starts to transmit
the voice
signal to the handset
and the handset
microphone
tone
to the circuit.
.
D305
is the protective
diode
to prevent
inputting irregular voltage to IC301.
2-3. Call : Speaker
When the speaker button is pressed, relay RY301 is set from the ringer side to the call side. The voltage is input
to D801 through hook switch S301 and RY301
and will rectify and reach R303 and Q301. R303 is connected to
the base of Q302 and sets it to HIGH.
Q301 becomes ON and the circuit voltage reaches speech network IC301. The output of speech network IC301 is
amplified by IC401 (1/4) and the main amp IC403, and drives the speaker.
For voice transmission, the voice signal from the microphone is amplified by IC501 (1/2) and IC501 (2/2), input
to
speech network IC301 through CODEC
IC (IC803), and transmitted to the circuit through Q301 and D301.
2-4. Dial : Handset Call
Dial comprises
of two types
: pulse and tone. The pulse type has lOpps. and 20pps. The dial type is preset by
switch S840.
This
dial differs
when
the telephone
is connected
to a commercial
use power
supply
or not.
When the telephone is not 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 phone S920, S921, $922,
$924, $925, S926, $927, S928, S929, S930, S931, and S932 when the power supply is cut off, dialer IC and the IC902
pulse signal outputs
High, Low
corresponding
to the dial signal. This signal activates
Q302 and Q301, intermits
the circuit
current
and. transmits
the pulse signal.
—20—
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