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When
the
second
tone has
been
received
(Tone
B
or
lone
C)
before the
one-strot
has tj-ned
out,
the
latch is set
and,
Dll
i.s
gror:nded,.
lhis
ciuses
Pin
14
of
IC2OL
to
go low
turaing
off that the
squelch
switch,
which t'r:rns on
Q209
ttrus
unsquefcfiing
the
radi.o.
2-7
LAmP
LoGIc
AND rGNrrER DRlvEs
!{hea
a signal is
decoded and
Pin
Dll
goes
1or, it sets the latch Pin 6,
IC2O6C
trIotlrlf,
Pin
4..I.C2OAB
"Iligh",
thereby tuza.ing on both ttre high rate'rALgRTo flasher
consisting
of
IC205D
and IC206tr and
the
two
igniter drives. lfie
user nay
select, via
a
juaper
pin'
which drLve he
requires eittrer pulsed
or
unpulsed.
Ehe loqr
on
Pin
6,
IC2O6C
disables both the;A€ on
logic
consisting
of
IC2O4A
and
ttre low
battery
i-ndicator
consisting
of
IC204B.
CI2O5F
and
IC2O5C
are
the
slow
light logic circuits for
the
low
battery
iJrdlcator..
A11
of
the
logic
eLeneots
activate the
LED
on
the front
panel by fo:*rard biasing
Q2l1
i:rto
conduction.
2-8
DEcoDER
RESET
Resetting
the
decoder
is
accougrlished
by
driving Pin
13
of
IC303
to
less
ttran lV
for at least 25os.
Xhis uay be
done
in
three
eraysr
the
carrier
controlled
reset,
tlre
t:ine out
reset
and
front
panel
sltiteh Sl{405.
The
front
panel switch
j.s
t}re only
way
to
reset botb the signal
light
and
the
decoder.
a
junper
is
i.nstalled
at
the factory
fro fiI-Dls to
,IU-D13.
Ttrj.s
allows the
decoder
to
reset
in
the
absence
of
a
carrier
so tbat.
it
crn be ready
to
decode
the next
nessage.
The
flashing
ligbt indicating
thae
the radio
has already received a
messaEe
nf,rst
be
reset nanually
via
Slf405
To
nonitor the radio traffj,c for
30 sec
to
3 minutes
a.fter a
:Bessage
has
been
received, switch
the
juugter from
fi-D15
to
JII-D14 and
set
the
RC
tiuring
net",!ilork
R293
for
the time
you
Cesire.
when
the
circuit
has timed
out,
Q214
will
stop
conducting
making
the
base
of
Q304
go
high
causing
it to
conduct and tbereby
resetting the
decoder.
Again
the flashing
light will
renain
on
rrntil
manually
reset
to let
the user
know
a
message
has
been
received.
!'lCA 6L1
-3-
SECTION
2
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