Hardware and Software Installation
Rev 1.4 Apr.08
27
Note: Do not install an on/off
switch on the main (red) battery
line, or connect the white ignition
sense wire to the red battery
wire. Both configurations bypass
the MP modem's controlled
shutdown sequence, and may
cause data loss and subsequent
power-on problems. Incorrect
wiring may also drain the vehicle
battery.
The
MP
modem’s
power
on/off
is
controlled
by
the
ignition
sense
line
(white
wire)
using
internal
software,
rather
than
a
hard
on/off
switch
on
the
red
power
line.
The
red,
black,
and
white
wires
connect
to
the
battery
and
ignition
switch
as
shown
in
the
power
harness
wiring
diagram.
Note: The battery cable used for a car, truck, or other mobile
connection must be less than 3 meters in length.
Figure 3-7: Wiring for the power harness.The white wire is the ignition sense.
•
When
the
white
ignition
sense
line
is
pulled
high
(5
to
36
V),
the
MP
modem
powers
on.
•
When
the
ignition
sense
line
is
pulled
low
(less
than
2
V),
the
MP
modem
performs
a
controlled
shutdown
sequence
(under
software
control),
de
‐
registering
and
saving
any
relevant
operational
data
before
powering
off.
Ignition sense options
There
are
three
ways
to
connect
the
ignition
sense
wiring:
•
Engine
on
only.
Connect
the
white
ignition
sense
wire
to
the
vehicle’s
ignition
switch
so
that
the
MP
modem
is
powered
on
only
when
the
ignition
key
is
switched
to
the
full
“On”
position,
that
is,
when
the
engine
has
been
started.
In
this
configuration,
the
engine
must
be
running
for
the
MP
modem
to
be
on.
—or—
•
Accessory
on.
Connect
the
white
ignition
sense
wire
to
the
vehicle’s
ignition
switch
so
that
the
MP
modem
is
powered
on
when
the
ignition
is
switched
to
“Accessory”
mode.
In
this
configuration,
the
MP
modem
is
on
whenever
other
vehicle
electrical
devices
can
be
switched
on
—such
as
when
the
radio
and
windshield
fan
can
run.
Black unfused wire
(Ground)
White wire
(Ignition sense)
Red wire
(Battery)
MP modem
5 A fuses (on red
and white only)
Switch (vehicle
ignition key, or
separate)
Vehicle battery
Summary of Contents for MP 881W
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