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6. AUTO STOP SIGNAL DETECTING CIRCUIT
SN
SIGNAL METER (13)
M
zg
x
|
8
Fe
FOR DISCHARGE
Ic2
1 3
a
R142
LAI235
|
>
&
470K
|
MUTE ((2)
6) 1C9 AT-600
(AUTO STOP)
AF ouT(6)
arene
|
NARROW BAND NOISE AMP
(OVER 100KHz)
AM SIGNAL METER
IC6 LAI245 (6)
tc2
sm (3)
LAI235
DIFFERENTIATION
MUTE (12)
67) 1C9 AT-600
(AUTO STOP)
AF ouT(6)
ane
IC6 LAI245 (6)
Fig. 9
1) During scanning in FM mode IC2 (3 is "L" and IC2
d2 is "H", and the output of Noise Amp. becomes
""H"' due to the detuning noise. Since NOR Gate con-
sisting of diode and inverter performs "H" output
only when all the inputs are "L"', the present output is
"1
Ifa broadcast is received, (3 becomes "H"', 42
becomes "'L" and the output of Noise Amp. becomes
"L" since detuning noise disappears.
Therefore, all
the inputs of NOR Gate becomes "'L" and the output
becomes '"'H".
"H" output of NOR Gate is differen-
tiated and reversed to make
@
terminal
of IC9
(AT-600) "L" and stop scanning.
IC6 (6 is always
"L" in FM mode. Auto Stop Signal in AM mode uses
the signal meter output of IC6 ( . IC6 4) is "H" at
the time of broadcast reception and is "L" on other
occasions.
Since IC2 43 is always '""H" in AM mode,
the output of NOR Gate is "L"'.
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