Car owners guide to: Car Audio > Wiring Interfaces & CAN bus

Perhaps you've decided that it's really not worth paying money to have your old radio unlocked and it's a good time to upgrade. But you don't want to lose the remote controls of your factory fitted stereo. Thankfully you can have a new model fitted and keep the factory-fitted convenience features by using an interface that will allow the non-standard radio to integrate perfectly into the dashboard and with the car manufacturer's wiring.

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 often use what's 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 adapters eliminates having to cut wires in the vehicle, and that 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 unit to work. 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 CD player to communicate with the factory-fitted amplifier; allow a factory radio to communicate correctly with new amplifiers; or maybe 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 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?

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. It has lots of uses in-car, but the most popular one is for providing a convenient solution to the need for hands-free mobile phone operation.

Bluetooth can also be used to stream music from one device - such as a Music Phone or portable MP3 player - to a Bluetooth-Ready car stereo system, or to wireless headphones/earphones. This makes use of Bluetooth's A2DP (Advanced Audio Distribution Profile) to wirelessly send the music from one device to the other. With more and more phones able to store and play music files, this is likely to become an increasingly useful feature in the future. But beware. Just because a phone says it has Bluetooth on-board doesn't mean it will stream music files. Apple's iPhone®, for example, currently only supports the Hands-Free Profile (HFP) and Headset Profile (HSP), but not A2DP, so it won't stream music wirelessly to Bluetooth headsets or a stereo system. In the case of the iPhone and iPod, you need to look to one of the dedicated in-car adaptors.

iPod™ & MP3 players

Portable devices such as Apple's iPod™, Touch and iPhone™, and the countless other MP3 and digital music file players on the market, have become many people's main way of storing and playing their music collections. The size and convenience of these players ensured they won a huge slice of the music player market, and while originally intended for use with earphones while 'on the move', there is now a large industry catering for add-on devices such as speaker systems and docking stations.

Not surprisingly, many people want to be able to use their digital music players in-car. There are lots of ways to help you integrate your player both electrically and physically, from simple cassette deck adaptors to wired and wireless docking stations that make it all very neat and tidy. Ask your local InCar Expert for advice.

Beware - it's seldom an easy wire-up job

You might think that the automotive industry would have moved towards completely standardising electrical systems, and that everything must be simpler now. Almost the opposite is true, in part because of the extra sophistication and variety of equipment fitted to today's vehicles.

With many modern cars now using a digital data bus control system (known as the Controller Area Network or CAN bus system), the need for professional advice and specialist in-car interface devices has never been greater.