In 1992 the US National Radio Systems Committee issued the North American version of the RDS standard, called the Radio Broadcast Data System. The CENELEC standard was updated in 1992 with the addition of Traffic Message Channel and in 1998 with Open Data Applications and, in 2000, RDS was published worldwide as IEC standard 2011 the xRDS Project: , the(first presented 2010 at the RDS-Forum). The Extended Radio Date System (abbreviated xRDS) is a solution with which broadcasters can multiply the speed of data transmission in the FM channel in a simple but compatible way. By using further normal RDS subcarriers, shifted into the higher frequencies in the FM multiplex. the mpx spectrum and carry the extra data amount which can be used for arbitrary applications. thay came out with the boombox and portable cassette or CD player with two or more loudspeakers and this devices and
The head unit is the centerpiece of the car's sound system. Typically located in the center of the dashboard, modern head units are densely integrated electronic packages housed in detachable face plates. As high-end head units are common targets for theft, many head units are typically integrated into the vehicle's alarm system.
Head units give the user control over the vehicle's entertainment media: AM/FM radio, satellite radio, CDs, cassette tapes (although these are now uncommon), MP3, GPS navigation, Bluetooth, etc. Many audio-only head units afford the user precise control over detailed audio functions such as volume, band, frequency, speaker balance, speaker fade, bass, treble, EQ and so on,
Several OEMs such as General Motors are integrating more advanced systems into vehicle's head units such that they can control vehicular functions such as door chimes and even offer vehicle data such as trouble warnings and odometer information; such a head unit thus serves as a secondary instrument panel.In as much as head units are a central part of a car's decor, they vary as widely in aesthetics as they do in functionality.With the advent of GPS and DVDs head units with video monitors and
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