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7 .0
SPECIAL ACCESSORY
EQUIPMENT
7
.1
End-of-Tape
Sensing Switch
7
.1.1
Description
The
end-of-tape
sensing
switch is
designed to provide a
contact
transfer to
indi-
cate
the end
of
a tape
regardless of
its direction
of
movement. Either the "make"
or
"break"
signal
may
be
used
depending
upon
the
logic requirements
of the system.
7 .1.2
Mechanical Operation
(See
Figure
20)
A lever
actuated sensing switch is
mounted
on the
inside face
of the
read
head
stripper
plate
.
The r oller
on the end of
the
switch actuator protrudes
through a slot in
both
the
stripper
plate and tape pressure
guide.
When
tape
is under the
tape guide, the switch contacts
will
be
transferred to
the
normally
open
position due
to
tape pressure against the switch actuator.
·
When
no
tape is
present, the switch
contacts
will be
in
the normally closed position. One sensing
switch
is positioned
on each side of
the
capstan
so
that end-of-tape
is indicated whether
tape
is
moving in either the forward or reverse direction.
7
.1.3
Electrical Operation
The sensing switches use form
"C"
contacts,
and as shown in
Figure 19,
contacts
are in the normally
closed
(NC) position
when
no
tape is under the
pressure
guide.
-
-
-
-
" - " '
r
A
-
-
-
""
(
''
)
(
II
)
N~
r, ;
0--
io~
--;J~
Figure 19.
Schematic
Showing
Switches
Indicating End
of
Tape
Alternate
logic
for
"end-of-tape"
switching may be easily arranged by removing
the
stripper
plate,
disconnecting the wires from the NC switch terminals,
and
reconnecting them
to
the NO terminals
.
7
.1.4
Adjustment
The roller
on
the switch actuator should protrude through the stripper plate 5/64
inch, so
that when
tape is
moving under the tape pressure guide, the
switch
will
be
closed. This
SCATTlC
Page 17
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