User's Manual

5
The MDC power leads should be crimped onto the power leads at the power input to the
communications device. Installing the power leads in this way will avoid the possibility of
the ground potential at the MDC differing from the ground potential of the
communications device (due to current draw during a transmit cycle).
If the MDC is connected to switched ignition power the units manifest will be lost every
time the engine is turned off. In some systems, the terminal will be connected to ignition
power and will be powered on and off automatically. If the ignition is off the terminal can
be powered using the power switch.
The MDC has a 2-amp fuse on its power input. The fuse is easily accessible via the back of
the unit if it needs to be replaced (port 2A in Figure 2). Note, however, that a blown fuse
will often indicate that there is either a problem with a connection to the MDC or with the
MDC itself. Check all connections before replacing the fuse.
Please refer to the Technical Data section of this manual for details on the voltage and
current requirements of the MDC.
Communications Device
There will also be a communications device that will have to be installed in the vehicle. In
radio systems, this will be a mobile radio with its accompanying antenna. If a data system
such as Mobitex or CDPD is being used, then the communications device will be a
modem. The size and location of the communications device should be taken into account
during the installation process to ensure that there is enough space to mount and install all
components of the system in the vehicle.