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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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