cone
1 pin 4.
Thus
the
key
scanning
from
CPU
detects the
shift
key
being not depressed.
3.08
Buzzer
{Circuit
Diagram
F)
The
buzzer is operated
by
a single shot multi-vibrator consisting of
_the
lower
2
NANO
gates of the
IC
8.
The
CPU
{IC
4)
applies a L-impulse to the multi-vibrator
from
the
pin 34. A H-level is
formed
for about 0.5
second
at
the pin 3 of
IC
8
and
operates the
oscillator
{higher 2
NANO
gates)
which
activates
the buzzer
BUZ
via the
transistor
Tr
2.
3.09
Hammer
solenoid, Impression
{Circuit
Diagram
F)
L
10
The
CPU
{IC
4)
applies continuously H-level to
its
pin 31.
The
base of T
23
comes
to L-level via
one
of
TRA
1.
It
locks
and
keeps the
hammer
solenoid.
The
pin
31
of
CPU
comes
to L-level for
character
printing.
The
base of
Tr
23
comes
to H-level with
+5V
from
Tr
6.
Then
the current
from
+36V
flows to the
magnet
coil via
the
cone
5 pin
a8
and
to the
collector
of
Tr
23
from
another
end
of
the
magnet
coil
via the
one
5 pin
b7.
Thus
the
striking
of plunger
for printing is activated.
After
striking,
the
Zener
diode
ZD
6 limits the fly-back voltage
to
51
v.
The
current flows the solenoid for constant printing is limited
by
the
Tr
30
under
the control of the
Tr
23
base.
The
total
printing
impression
can
be
adjusted
by
the variable
resistor
VR
1,
which
changes the
volume
of current flowing to the
hammer
solenoid.
Impression
The
different
type contour of characters is considered
so
that
the
current will
flow
to the
hammer
solenoid for a
different
time.
It
is
divided into 3 stages:
Normal
- Strong
All
normal
capital
and
small
letters
and
symbols.
Large
space
letters
{for
example
Ww
Mn
& §).
Small
space
symbols
{for
example
,.-_
1
).
-
Weak
The
necessary time for the concerned characters are
filed
in
the
ROM
of
CPU
or
EPROM.
It
controls
the
output time of L-level
from
the
CPU.
The
print
impreision
can
be
selected with the
slide
switch
on
the
keyboard
according to the.
number
of copies.
It
also controls the
output time of L-level
from
the
CPU.
• Position 1
Normal
impression
No
contact
and
therefore
no
signal to the
CPU.
e Position 2
Higher
impression
Slide switch contact
S2
in
the
keyboard
matrix is closed.
The
CPU
detects
it
by
key
scanning
as
described
in
paragraph
3.03.
_l
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