OEM hands-free kits (HF) are installed in the vehicle completely hidden. It is usually installed in the dashboard of the vehicle and is connected to the original car radio. These OEM hands-free sets usually behave similarly to the original HF sets and can in most cases be controlled with the original buttons on the steering wheel or under the steering wheel. Many of these OEM HF sets also have additional inputs, for example for an iPod or a USB input. Before buying, you need to check whether your original car radio has a CD changer input. When making a phone call, you need to switch to the media or CD changer, then you can make a call via the OEM HF set. Most HF sets come with an external microphone that must be installed in the car.