set-up instructions is provided with each device.
(b) The firing device consists of a number of
6. Fasteners, a set of nails and screws, for
different components to facilitate operation in its
securing the switch are included with each
device. When required the switch can be secured
to a tree limb or similar object with a tie-down
s ring loaded tiring pin held in position by a mov-
wire, a special hole is provided in the switch for
able sear plate that can be set to release the tir-
ing pin in an one of the four operating modes.
(c) The olive drab plastic switch and
(a) The operating mode is deter-
coupling body are unpainted. They are
mined by selective removal of one of the two
unmarked except for a yellow band painted on
pivot pins in the switch which permits the sear
the coupling body. The brass safety pin and steel
late to rotate about the other pivot pin. When
pivot pins are unpainted.
both pins are in place the sear plate is locked in
(d) The M142 firing device components
position. The two pivot pins (round head pivot
in addition to the instruction sheet, screws and
pin and square head pivot pin) are of different
nails are packed in a cylindrical metal container
3-1/8 in. diameter and 1-1/4 in. high. Fifty-six
(b) When the switch is set for pull or
containers are packed in four M19A1 ammuni-
pressure (by removal of the square head pin) a pull
tion boxes (14 per box).
of more than 4 pounds or a pressure of more than
9 pounds makes the sear plate pivot on the round-
g. Fuse, Blasting, Time. Time blasting fuse
head pin, releasing the spring loaded firing pin.
transmits a flame from a match or igniter to a
(c) When the switch is set for pres-
nonelectric blasting cap, providing a time delay
sure release (by removal of the round-head pin),
wherein operators may retire to a safe distance
the sear plate is held down by a load of at least 2
prior to the explosion. There are two types:
safety fuse and time blasting fuse M700. These
lb. Removal of the 2 lb load makes the sear plate
pivot on the square-head pin, releasing the
may be used interchangeably.
spring loaded firing pin.
Safety time blasting fuse is used in general demo-
(d) When the switch is set for ten-
sion release (by removal of the round-head pin),
litions. It is in the form of a cord and has a black
the sear late is held under tension by a taut trip-
powder core covered with several layers of fiber
wire. Cutting of the tripwire makes the sear
and waterproofing material, usually orange in
plate pivot on the square-head pin, releasing the
color. The burning rate may vary for the same or
spring loaded firing pin.
different rolls from 30 to 45 seconds per foot
(e) A safety pin is incorporated in
under different atmospheric and climatic condi-
the switch to prevent accidental initiation. It is
tions. Each roll must be tested prior to using in
positioned in front of' the firing pin and is only
the area where the charge is to be placed.
removed after the desired operating mode is set
Particular precautions must be taken if used
under water, as the rate of burning is increased
2. The tripwire consists of 50 feet of cop-
significantly Accordingly, each roll should be
per wire wound on a cardboard or plastic spool.
tested under water prior to preparation of the
The olive drab coat of paint over the wire pre-
charge. In arctic temperatures, the outside cover-
vents it from accidentally unwinding and aids con-
ing becomes brittle and cracks easily. Safety time
cealment. A retaining clip on the cable reel
blasting fuse is packed as follows:
assembly (spool of tripwire) is on later produc-
(a) 50-foot coil, 2 coils per package, and
tion items. This clip is given for convenience to
30 packages (3,000 feet) in a wooden box; weight,
prevent remaining cable from unwiding.
Tripwire is used in the tension release mode and
(b) 50-foot coil, 2 coils per package, 5
in the pull mode.
packages sealed in a metal can, and 8 cans (4,000
3. The tension release attachment is a
feet) per wooden box. The weight, 93.6 pounds.
special formed stainless steel wire that has a
(c) 50-feet coil, 2 coils per package, and
action. In the tension release mode
60 packages (6,000 feet) per wooden box; weight,
the attachment holds the tripwire under tension
1 6 2 pounds.
that, in turn, maintains the firing device in a con-
Actuation is initiated
stant armed position.
Time blasting fuse M700 is similar to safety fuse
when the taut tripwire is cut which permits the
and may be used interchangeable with it. The
sear plate to release the firing pin.
fuse is a dark green cord 0.2 inches in diameter
4. The coupling body is a cylindrical plas-
with a plastic cover. Depending on the time of
tic assembly that contains the explosive
manufacture, the cover is smooth or has single
initiating element, and M42 primer, but no blast-
bands around the outside at 1-foot or 18-inch
ing cap . The coupling body is interchangeable
intervals and double bands at 5-foot or 90-inch
with the standard coupling base in functioning
intervals. These bands are provided for easy
measuring purposes. T h e burning rate is
tion, has the alternate capability of lighting a
approximately 40 seconds per foot. The burning
The coupling body has
time blasting fuse.
rate however must always be tested in the
another advantage over the standard coupling
same manner as the safety fuse. Time blasting
base in that it is not necessary to crimp the blast-
fuse M700 is packed in 50-foot coils, 2 coils
ing cap to attach it.
per package, 5 packages per sealed con-
5. An instruction sheet giving abbreviated