Car owners guide to: Car Audio > Wiring Interfaces & CAN
bus
 You've
picked out the new in-dash CD player that fits your budget and then
you're told that other parts are needed. Those "other parts"
are usually wires and other not-at-all-sexy bits you'd really prefer
not to have to buy. You may even wonder if the sales person is selling
you something you don't need. But these items are vital in making
sure your new in-car player is installed so that it integrates perfectly
into the dashboard and with the car manufacturer's wiring.
Here are a few things you may need, and why
Mounting plates and wiring interfaces not only ensure your new
car CD player will sit nicely in the dash and perhaps use the existing
steering-wheel mounted controls, they also mean it can be removed
without a trace if you later change the vehicle.
Here are a few questions you may be asked, with explanations to
help prepare you.
The salesperson says I need a mounting kit. What is a mounting
kit?
A mounting kit is what physically attaches your new CD player to
the dashboard of your car. In all but a very few cases, the size
of the new player will not match the size of the factory radio.
The mounting kit allows for this difference in size, allowing your
new player to be safely and neatly attached to the substructure
of the dashboard.
I'm told I need some type of wiring harness. Isn't it just a standard
fitting?
Each vehicle on the road has its own style electrical connectors,
wiring colours and pin configurations. Often, different trim levels
of the same vehicle results in different wiring and connectors.
Trained installers will very often use what is called a harness
adapter to make the job faster and more reliable. This harness adapter
is a plastic housing with electrical pins in it, which matches the
harness connector in your car. Using one of these harness adapters
eliminates having to cut wires in the vehicle. This in turn helps
to avoid vehicle warranty issues and allows the wiring to be returned
to the original factory state at any time.
Additionally, most antenna connectors in new cars and goods vehicles
do not match the antenna connectors found on aftermarket CD players.
Those units do use a standard connector, but the motor manufacturers
use about 10 different types of antenna connectors, and an adapter
is required to match each of these to the standard one that is used
by all aftermarket manufacturers.
I'm told I need an OEM-Integration Interface for my new CD player
to work correctly. Do I really need it?
OEM is short for 'Original Equipment Manufacturer' - this is a
term industry people sometimes use when referring to the vehicle
manufacturers. As the name implies, OEM-Integration is the process
of integrating new equipment into, or onto, a vehicle.
Your MMSA specialist uses an OEM-Integration Interface to make
a piece of aftermarket car audio, video or Sat Nav equipment match
up with something that is already in the car, having been installed
by the OEM at the factory.
These interfaces can have a variety of purposes. They can allow
your new car CD player to communicate correctly with the factory
amplifier; they can allow a factory radio to communicate correctly
with new amplifiers; or they may allow the audio-control buttons
on your steering wheel to control a new CD player.
More advanced interfaces allow aftermarket in-car CD changers to
be connected to, and controlled by, a factory radio. One of these
sophisticated digital interfaces can help you save hundreds of pounds
by not having to buy a factory-specified CD changer.
If your vehicle uses a digital data bus (CAN bus) control/communication
system at the heart of its electronics, a specialised OEM-Integration
Interface will be required to handle the data protocols correctly.
 Bluetooth
- what is it?
In a sense, Bluetooth technology is also a kind of interface, but
without wires. It's a method of wireless communication capable of
transmitting data over short distances and was developed as a way
of connecting many different types of electronic equipment without
the need for cables. Bluetooth provides a standard so that machines
from different manufacturers will happily "talk" to each
other.
When Bluetooth connects devices to each other, they become "paired"
- in other words they each check that they are compatible and will
be able to exchange data. The user can set a secure level so that
connections can only be established between allowed devices - a
work colleague's computer and your own laptop PC for example, to
allow secure exchange of sales figures.
There are many uses for Bluetooth. Your wireless headset can be
connected to the mobile phone in your car or briefcase for hands-free
use, and your handheld PDA can automatically synchronise with your
personal computer when you walk in the office. But that's just the
beginning and Bluetooth opens up a lot of possibilities.
 Summary
You might think that the automotive industry would have moved towards
completely standardising electrical systems, and that everything
must be simpler to interface now. Almost the opposite is true, in
part because of the extra sophistication and variety of equipment
fitted to today's vehicles.
A good rule of thumb is that the newer your car or commercial vehicle,
the more heavily your installer will have to rely on an OEM-Integration
Interface to complete the installation of in-car entertainment or
Sat Nav equipment.
With many modern cars now moving to a digital data bus control
system (known as the Controller Area Network or CAN bus system),
not helped by a distinct lack of standardisation between different
motor manufacturers, the need for professional advice and specialist
in-car interface devices has never been greater.
Some vehicles may even require two or three separate interfaces.
And where in-car communications are being fitted, Bluetooth provides
a convenient solution to the need for hands-free operation and an
alternative to having a remotely mounted microphone and speaker
fitted.
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