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Fig. 4-4 Scan control circuit
Preset Memory
Preset memory
(in TC9137P) allows 6 FM band
and 6 AM band stations to be placed in memory.
Pins 13 through 19 of TC9137P are input/output
type terminals used by the' display driver.
Whena
low level input is applied momentarily
to pin 13
(STO), memory
write may
be performed for a
few seconds.
During this period, if one of the pins
between 14 and 19 (M1—M6) is designated (by L
level input) as the memory address, the frequency
on the display at that time is stored in memory,
and the corresponding memory
address indicator
(STATION 1-6) is illuminated.
When this sequence
is completed, the memory write status is released.
If a memory
address is not designated within this
few-second time period, the memory write status
will automatically be released.
Preset memory is
automatically
switched between the FM and AM
band along with regular band switching.
Memory
write status is indicated by the AM or
FM
band indicator going from an illuminated to
a
flashing status.
The cathode for the indicator
LEDs
uses
a common
circuit,
and
switching is
performed by Q63.
Q63 is driven by an astable
multi-vibrator
that
consists
of
two
inverters.
Normally,
this multivibrator
is cut off by +B3
supplied through R229, and this maintains Q63 in
an ON
status, lighting either the FM or AM
in-
dicator.
When
the
MEMORY
switch
is placed
on,
a low level input is applied to pin 13 (STO).
This causes D45
to conduct, inhibiting +B3 and
causing the astable multivibrator to operate, turn-
ing Q63 on-off and causing the FM (or AM) band
indicator
to flash.
Even
though
the MEMORY
switch is turned
off
(by releasing the MEMORY
key), the low level input at pin 13 (STO) continues
(memory write status held) and the FM (AM) band
indicator continues to flash.
TCRI37P
Q58~
O61
FM/AM
BAND
SWITCHING
DETECTOR
REC
LEVEL
CHECK
Fig. 4-5 Memory store/call circuit
Memory
recall
is by designating
one
of the
memory address pins between 14 and 19 (M1—M6).
This applies a low level input to the pin causing
the
broadcast
frequency
stored
in that memory
to be tuned to and illuminates the corresponding
indicator.
When the band is switched between FM and AM,
a signal from
the band
switch
detection
circuit
causes Q57 to momentarily come
on, and tuning
automatically
goes
to the
frequency
stored
in
memory 1 (STATION 1).
Memory Hold
The power switch (ON/STANDBY)
for the F-9
is located in the second stage of the power trans-
formers (Fig. 4-6). Power continues to be supplied
to TC9137P even after the power switeh is tured
off (in STANDBY position).
TC9137P
has a self-contained inhibit function
allowing it to set all its functions to a static condi-
tion
(oscillations
stopped,
all inputs locked, in-
dicator drives turned off, all outputs set to L level).
1
lis
ro
RECTIFIER
rate
A
ei
O)
POWER
TRANSFORMERS
Fig. 4-6 Memory backup circuit
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