Specifications

FCS1362 Page 43 of 74 © Nov 2010
The supply cable from the radio equipment should approach the battery in such a way that when
terminated the two wires cannot be inadvertently reversed e.g. one wire is shorter than the other.
It is recommended that unless a moulded twin supply cable is used then the two supply lines be run
together along their length in order to reduce induced noise.
4.6.2.1. Installing power supply cable
When fitting a supply cable, the following should be considered:
• heavy duty cable should be used on long cable runs to minimise voltage drop
• the cable should be of a higher current capacity than the protection fuse and the correct fuse fitted
• the cable should be as short as possible
• routing and mounting of the cable should follow advice in section 4.3.1
• the supply cable run should, where possible, be separate from that of the ICE equipment control
cables, although they may pass through the same holes in the chassis and body for ease of fitting.
o Suitable grommets must be fitted if additional holes are drilled see section 2.11
• the power cable should be sited away from ignition coil, HT circuits and ECUs, antenna coaxial
cables and, where possible, other vehicle wiring.
4.6.3. Fusing
The power supply cable should only be fused in the positive power line with the fuse located as close as
possible to the battery or power source.
Fuses must not be used in parallel as a means of obtaining a higher rated supply.
For external connections use water-resistant fuse holders and ensure fuses comply with the equipment
manufacturers recommended rating and type.
Fuse ratings must not be increased to accommodate higher power equipment to such a point that the
wiring of the vehicle and/or the equipment is no longer protected.
4.6.4. Negative Feed Connection
In the case of negative earth return vehicles, the negative power line should not be fused. It should be
connected to the vehicle body as close as practical to the point at which the battery-to-body connection is
made. Do not connect the negative power line directly to the battery.
For heavy commercial vehicles (>7.5Tonne GVW) only, and those vehicles with tilting cabs where the
cab may be isolated from the chassis by rubber mountings, a ground point is provided by the vehicle
manufacturer within the cab to provide battery to cab grounding. Generally this is located within the main
fuse box. It is recommended that this point be used for installations in this instance.
With certain equipment it may be necessary to connect the negative supply line to a local earth point. In
this case an existing vehicle earth point must be used.
4.6.5. Sourcing ignition sense
Many types of equipment have provision for ignition sense.
The ignition sense facility can enable the equipment to be powered on and off with the ignition. It should
be noted that some equipment can be programmed to have a "delay off" function to allow it to remain on
for a set period, after the ignition is switched off. See section 2.7 for information regarding using the
CAN bus to provide an ignition sense.
4.6.5.1. Provision of ignition sense from an ignition feed
There may be no ignition sense present on the vehicle’s original wiring harness plug to which the
equipment is connected. When this facility is required the equipment’s ignition sense should be
connected to a positive feed controlled by the vehicle’s ignition switch, where such a suitable feed is
available.
Consult with the vehicle manufacturer to determine a suitable source feed for ignition sense.