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KRC-851D
CIRCUIT DESCRIPTION
Operation Description: EXT. MUTE
(1)
(2)
Connections:
The "MUTE
IN1" and "MUTE IN2" are connected to
the core wires (red and white) of the 2-conductor
shielded cable.
Connect these core wires to the speaker terminals of
the telephone
set. (Shielding jacket should
not be
connected to anywhere,)
Circuit Operation:
When there is a ringing on the speaker of the tele-
phone set, the ringing signal is applied to the buffer
of IC6 via the filter consisting of R93, R94, C91
—
C94, R38 and R39 and the protection diode consist-
ing of D1 and D2.
After passing through the buffer, due to the balanced
input signal path, the only difference
components
between IN1 and IN2 will be amplified (in IC7). The
DC
components
are eliminated,
and
the AC
level
signal is rectified by the rectifier circuit consisting of
D3, C25, R46 and R47 to convert into the DC level.
Then, the signal is inverted by Q3 and R234 to be
supplied to the port of the microcomputer.
R49 and
C26 are used to set the time constant so as to delay
the response.
(xX08-2412-70)
03
IN
PORT
| EXT. MUTE IN
{X14-2852-70)
Ic7 (2/2)
(3) Operation on the Unit:
When
the
microcomputer
detects
the
EXT-MUTE
signal, the unit enters the all-off status while "CALL"
appears in the display.
To restore from the "CALL" status, press the PLAY
key of the source connected.
Tuner ............ TUNER/PWR key
Tapes
evades. setene PLAY/PROG key
CD; CH
s ieeies PLAY/PAUSE key
1C6(2/2)
7.5V
|
|
O
GND
MUTE
MUTE
IN2
INI
(X89-1142-70)
|
{F/6)
11
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