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Ericsson DIALOG - Dial Unit Design and Operation; Instrument Case Materials and Ergonomics

Ericsson DIALOG
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3.4
Dial
unit
12
3.3.4
Varistors
Dialog
has
a
number
of
varistors
(13 C), one
working
as
shock
absorber
for
the
receiver
and
the
others
as
part
of
the
equalizing
network.
The
varistors
are
voltage
dependent
,
non-linear
resistors.
With one
exception
they
are
made
of
silicon.
The
exception
is
the
shock
absorber
which
is
made
of
selenium
and
moulded
in
epoxy
resin.
The
silicon-type
varistors
are
enclosed
in
glass
capsules.
Each
single
component
comprises
one
varistor.
Fig. 14
The
cradle
switch
springs
et
fitted
to the
insulating
sheet
3.3.5
Cradle-switch
springset
The
cradle
-switch
spring
set
(fig. 14)
consists
of 8
springs
(1)
with twin
contacts.
Together
with
insulating
spacers,
the
springs
are
mounted
directly
on
the
springset
frame
(4)
and
operated
by
a
cradle-switch
(3)
with
two
levers.
When
the
handset
is
lifted
a
tension
spring
(5)
operates
the
cradle
to
a
fixed
position.
On
replacing
the
handset,
two
plungers
are
depressed,
which
actuate
the
levers
and
the
cradle-switch
turns
over
to
its
first
position,
allowing
a
return
spring
to
reset
the
con-
tact
springs
via
a
lifting
comb
(2).
The
cradle-switch
frame
as
well
as
the
levers
are
made
of
sheet
steel.
Nylon
bearings
(6)
reduce
the
amount
of
friction
to
a
minimum
and
increase
the
life-time.
The
weight
of
the
handset
and
the
load
on
the
tension
spring
are
so
adjusted
that
good
function
and
a wide
margin
of
safety
are
achieved.
The
hook-switch
frame
contains
a
threaded
hole
for
the
single
screw.
by
means
of
which
the
instrument
is
opened.
The
dial
(fig. 15),
is
mounted
on
brackets
(1)
equipped
with
four
tabs
(2),
which
fit
into
four
slots
in
the
base
plate.
To
obtain
good
locking
effect,
these
four
slots
are
displaced
slightly
in
pairs.
The
covering
plate
(3) of
the
dial
is
furnished
with
figures
outside
the
finger
wheel
(4).
This
has
been
possible
since
the
plate
is
larger
than
on
earlier
conventional
types
of
telephone
instruments.
The
finger
wheel
is
made
of
transparent
plastic.
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