2.3 ENTERTAINMENT AND PERIPHERAL SYSTEMS

2.3.1 Integrated Communications

• Modern vehicles integrate audio, video and communication systems into a network. 
• This allows for a high quality, compact and ergonomic system, which combines entertainment features with simple operation.
• Controls are centralized with hardware, such as CD stackers, and DVD players located remotely.
• Communication between components uses a combination of hard wiring and data buses.
• With data buses being used, audio messages can be broadcast over the audio system that relate to other vehicle systems. For example, a voice message can say “the park brake is on” or “left rear tire is under inflated”.
• The system allows for features such as the interruption or replacement of audio entertainment when there is an incoming phone call, or simply muting the audio to allow a hands-free phone conversation.
• Audio control functions are usually located on the central control pod or on the component’s head unit. Vehicles can integrate the common audio controls on the steering wheel to allow for safer driving.
• The music played on a system usually comes from one of several sources. Magnetically on a cassette tape, optically on a CD or DVD, by radio frequency from radio stations or satellites, or from other portable devices.
• The information is decoded or processed by the control unit and outputted to drive speakers located throughout the vehicle.
• Another function provided by the body control unit is that of speed dependant volume.
• The control unit has an input from the vehicle speed sensor, which allows it to gradually increase audio system volume proportionally with road speed.
• As speed, and therefore engine and road noise increases, the audio volume will increase. As speed decreases the audio volume will decrease.
• Viewing screens for onboard TV, DVD and games can be located in the dash, however, if the screen is viewable by the driver it must disable when the vehicle is in motion.
• Control units can be hard wired, or wireless using an infrared remote control.

2.3.2 Body Controlled Lighting Systems

• When driving at dusk the ambient light can fade slowly. In some vehicles an ambient light sensor determines when light levels are low.
• This is read by the body control unit, which turns the headlights on.
• Automatic “dipping” headlights use a sensor located at the front of the vehicle to detect light from oncoming vehicles.
• If the headlights are on, low beam is selected automatically. This prevents oncoming traffic being dazzled by the vehicles high beam.
• Delayed “off” allows the headlights to be left on after the engine has stopped and the doors locked. The headlights will automatically extinguish after a period of time, allowing the driver to safely see their way from the vehicle.
• On some vehicles the body control unit will turn the headlights off if the headlights are left on after the ignition switch is turned off and the driver’s door is opened.
• On other vehicles headlight warning alarms sound if the headlights are left on after the engine has been turned off and a door is opened. This reduces the risk of the headlights draining the battery.
• The body control unit illuminates a warning light when an exterior lighting bulb such as a stop, tail or flasher light has failed.
• To do this, the body control unit compares current flowing through these circuits to values stored in the computers memory.
• If the current flowing is outside set parameters the warning light is illuminated.
• The body control unit can be programmed to keep the interior light illuminated after the doors have been closed for a set period of time, to allow the occupants to locate seat belts or insert the ignition key.
• It will also illuminate the light when the ignition is turned off to allow the occupants to locate door handles and luggage items.

2.3.3 Proximity Sensors

• A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. 
• A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets demand different sensors. For example, a capacitive proximity sensor or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target.
• Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between the sensor and the sensed object.
• Proximity sensors are also used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam turbines, compressors, and motors that use sleeve-type bearings.[1]

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2.3.4 Reflective Displays

• In a vehicle, conventional dashboard displays have a short viewing distance. 
• When the driver is viewing the road and then has to switch to look at the instrument panel, a finite time is required for the driver to adjust his field of vision (typically 0.5 seconds).
• During this time the driver cannot focus on the road or the instruments and this is a safety-critical aspect.
• Reflective displays or Head-Up Displays (HUD) are mounted within the dash panel. They use a mirror embedded in the dash, forward of the driver, to reflect an image of the instrument cluster.
• The actual instruments are hidden in the dash and it is a reflected view of them that the driver sees.
• This has the effect of the instruments appearing to be located further away than they actually are.
• Thus, driver’s focal point changes less when looking from the road to the instruments and back.