Head unit

A car radio is a radio receiver that is designed for installation in a motor vehicle. To this end, it usually has an operating voltage of 12 V and a standardized or adapted to a vehicle type fitted case. Compared to home appliances it is especially robust against vibrations and temperature fluctuations. In addition to the radio reception can usually also play certain phonogram, the first Internet car radio in 2009 was presented by the company Blaupunkt.

  • 2.1 From 1920
  • 2.2 From 1940
  • 2.3 From 1960
  • 2.4 From 1980
  • 2.5 From 1990
  • 2.6 2000 to today
  • 2.7 transmission paths


Current radios can receive stations on FM, medium wave, occasionally also on long wave and DAB, and sometimes on short wave. To support the driver's RDS are usually fitted traffic information decoder. More powerful devices also have dual tuner or TMC for textual display of traffic information messages. Sometimes navigation systems are also integrated. An anti-theft is common today.

By the beginning of the 21st century integrated cassette player were standard addition. These were replaced by the audio CDs. Many new models can read and assign external audio or USB ports, or readers for SD card or MMC cards and MP3 CDs and DVDs. Could not prevail against it MiniDisc player.

In Europe, over the counter car radios are usually offered in a standard case size that can be installed in accordance with recesses provided on the center console in the car. Modified to include factory-installed car radios, may be equipped with the same navigation system, most automobile manufacturers directly integrated into the center console in the meantime. The higher mounting position is to bring the device in more detail in the driver's field of view to reduce its deflection by the exchange of glances. To increase road safety, a remote control is provided in near steering wheel with factory -fitted radio too often, which allows adjustment of the radio without taking your hands off the wheel.

Measures according to ISO

The international standard ISO 7736 from March 1984 both housings and terminals for car radios are standardized for front installation in road vehicles. While a minimum of 160 mm is determined for the shaft depth, the front end is set at a width of 180 mm in two different height options (50 and 100 mm). This standard was established in April 1984 7736 implemented as DIN ISO in a national German and in September 1986 as ÖNORM ISO 7736 in an Austrian national standard (as of May 2013).


→ Main article: ISO 10487

The today's popular car stereos have generally standardized connector according to ISO 10487th Thus, the units can be installed independently of the manufacturer in any vehicle with ISO connectors.

In recent years, many vehicle manufacturers have started to bind their factory-installed car radios via special connections to the in-vehicle CAN bus. In these cases, the installation of car radios from a different manufacturer is connected to other costs that are incurred in the form of special adapter.

  • Ground or negative terminal of the voltage supply
  • Duration Plus 12 V voltage with respect to ground, even when the vehicle is parked, it is necessary to be able to listen to the radio when parked ignition or in some devices to save settings.
  • Ignition positive, 12 V with the ignition on, enables automatic switching on and off the radio on the ignition and steering lock
  • GALA input, receives the speed signal from the speedometer and allows a speed -dependent volume control
  • Antenna input
  • Lighting, 0-12 V, for the Night Switch the radio illumination or on some models adjustment of the illumination intensity corresponding to the illumination of the instruments on board the vehicle.

For aerial socket in car radios, there are two standards, the older and the newer according to DIN ISO:

  • DIN: Characteristic impedance: 150 ohms; Pin diameter: 3.2 mm; Pin length: about 13 mm
  • ISO: Impedance: 50 ohms; Pin diameter: 2.5 mm; Pin length: about 5 mm

In addition, there are often additional ports for CD changer, hands-free, remote control and external music sources. If there is no connection available for external sources, an adapter cartridge can be used. Since 2006, mini transmitters in the VHF range are approved, the audio signals transmitted (for example, an MP3 player ) via radio to the car radio. There are also devices that feed the audio signals by RF modulation in the antenna cable. Furthermore, are now offered specifically for original car radio adapter that emulate a CD changer to it to connect a storage medium with MP3 files or an AUX source.

More modern car radios often have an additional auxiliary input on the front or back in order to use it to connect directly external sources such as Mp3 player wired can. This is often realized in the form of a 3.5mm jack on the front, sometimes on the back with the aid of an RCA connector.

Most often feature modern car radio with four speaker outputs that deliver a power of about 15 watts RMS. Many manufacturers significantly higher music power is given, for example ( 4 x 50 Watts ), but this power rating is not standardized and thus leaves much room for interpretation. In Car- HiFi sector external power amplifiers are often used to achieve higher performance. This is (English Pre-Out ) connected with an RCA cable to the preamp output of the radio. Factory-fitted car radios generally have no pre-out, aftermarket radios are, however, depending on the equipment with up to 6 of these outputs equipped having a voltage level of approximately 1.5 to 7 volts. Higher output level process promising interference-free signal transmission. To be able to connect an amplifier to a car radio with no preamp output, it is possible to use a so-called Hi -Lo adapter. Such adapters reduce the voltage from the speaker output of the radio, so that a signal strength similar to a preamplifier output is produced.


Despite identical looking connectors according to ISO 10487, the pin assignment is inconsistent.

So mix up some automakers permanent positive and ignition positive in the vehicle connector, so in this case malfunctioning of the radio occur ( in this example, the radio is switched on permanently, and intended as a signal line ignition plus must take over the power supply of the radio, which can lead to overloading of circuits ).

Also, the connection speed is dependent volume adjustment ( landscaping ) fahrzeugseitg not always on the same pin in the connector set. Order to avoid a malfunction of the brake or the antilock brake system (ABS) and its extensions TCS / ESP, this signal is, however, produced separately from the speed-dependent signal from the ABS. All of the brakes and competent in related electronic signals may in principle be used for any other functions in the vehicle for safety reasons. This means that with a lack of in an older vehicle GALA signal this must not be taken from the ABS signal.

It can still happen more fahrzeughersterstellerspezifische contact assignments of the ISO plug, which can lead to disorders of vehicle electronics when connecting an accessory radio.

Thus - in legal terms - will go out by the non- professional and proper self- installing a car radio to use the vehicle. Therefore, some vehicle manufacturers forbid the legally binding instructions for the vehicles yourself installation of car radios.

The fact that the vehicle manufacturers connect their factory radio continues with the vehicle, the replacement can by a radio from another manufacturer also lead to the elimination of features that only through the factory radio had previously been reached (eg time setting, access to the on-board computer, failure of the steering wheel remote control).


From 1920

1922 radio was installed in a Ford Model T in Chicago, at the same time a Daimler was equipped with a car radio by Marco Iphone Co in England. 1927, the first industrially manufactured by the company Storage Battery Co., Philadelphia car radio " Philco Transitone " in the United States, Chevrolet was offered as an accessory. Galvin Manufacturing Corporation (GMC ) built in 1930, the first commercially successful car radio in the world. Developers were William P. Lear and Elmer Wavering. The model 5T71 cost 110-130 dollars. The radio was because of its heavy and bulky design, the name "Motorola", a word created from motor ( motorcar, motion) and ola (sound, wave, la ola ) (according to other sources of fire one: " A combination of automobile and Victrola, the legendary Gramophone "). The success was so great that it was soon in the United States became a synonym for the manufacturer and for a car radio at all.

From 1940

1949 was the first time, install the receiver on the car radio in the dashboard. The company Becker, (now Harman Becker Automotive Systems ), in the person of Max Egon Becker presented the medium wave device Autophon (5 tubes / 6 circles) and the additional long - and short- wave receiving Aerophon the client Mercedes Benz before, a long time business relationship begins. Blaupunkt had moved to the dismantling of the Berlin operation to Hildesheim and put the 5A649 before that are built into the instrument panel and so could dispense with the Bowden cable. 1951 led the company Becker with the device Nuremberg station buttons with inductive tuning ( variometer ) a. 1952 appeared the A52KU and A520KU (with or without pushbuttons) Blaupunkt who could also receive the established in 1951 FM broadcasting. 1953 held the VHF range ( in mono ) and the automatic channel search with the Becker Mexico collection. Blaupunkt introduced the improved A53KU. 1954 presented the model Blaupunkt Köln with automatic station search. 1957 began the use of transistors in the output stage and in DC-DC converter ( for the remaining electron tubes ). 1958 appeared to be affixed under the instrument panel 17- cm plates, juke car Mignon by Philips to meet the desire for his own music design in the motor vehicle.

From 1960

The first fully stocked with transistors car radio was introduced in 1961 by Philips, in 1963 there were of the Becker Monte Carlo, 1965 drew Grundig with the AS40 after. 1968 came the car radio with built-in cassette player on (Philips). In 1969 Blaupunkt the first stereo car radio Frankfurt on the market. Becker put a stereo cassette Radio Mexico Olympic stereo ( with mono reception and Stereocassette ) and the stereo radio stereo Europe before. In 1973 Blaupunkt before the full stereo cassette player Berlin, the operation was carried out by a remote gooseneck, which should bring the controls closer to the driver. In 1974, the driver broadcast information system ARI was switched on 1 June, which allowed the automatic detection of traffic reports on the car radio. The first ARI car radio was presented by Blaupunkt. Appeared in 1975, the Becker Mexico cassette full stereo reverse cassette operation with auto-reverse, the last in mechanical design ( ie voting, reverse operation). In 1976 the two Becker Europa Cassette courier courier and Monza came on the market, courier stands for the labeling of Traffic program ( ARI). 1977 brought the Blaupunkt Koblenz CB on the market with integrated CB radio, all in the DIN slot. 1979 Becker Mexico Electronic was controlled with a microprocessor, Blaupunkt delivered the Bamberg QTS with LED 7- segment digital display for the reception frequency and quartz tuning system.

From 1980

1980 renounced Becker Mexico Cassette Electronic at 385 knobs for volume and tuning and you can take out to the car radio theft protection. In 1982 Blaupunkt Berlin IQR 83 the front, with multi-line LCD display, automatic PCI transmitter identification and speech output, Grundig brought the WkC3867VD with a cassette drive and LCD digital display on the market. 1983 built-in CD player were presented instead of the cartridge drives, 1985, the devices appeared with integrated CD player from Philips and Becker ( the Mexico Compact Disc 860), later supplemented with CD changers. Car radios could be protected by a code number against theft, Philips equipment looked for the best incident channels within a radio network. In 1987, the Becker Mexico Diversity with two receivers, one for radio reception, the other for monitoring an RDS station. On April 1, 1988, the Radio Data System (RDS) for automatic processing of traffic information messages on the car radio, transmission of station name and other additional information was put into operation. The first car radio with RDS was the option of a Volvo in Volvo radio type SR- 701. The first devices showed the station name ( RDS PS ) and switched automatically to the best frequency (RDS - AF), for example, the Blaupunkt Montreux RDR 49th 1989 you could for devices Grundig detach the faceplate of the radio anti-theft protection, Blaupunkt has been used for a keycard.

From 1990

1991 RDS EON was used, that is, traffic could also be received when the set station spread no traffic, but communicates via RDS - EON, what else does that. 1992 has been made available with the Blaupunkt Stockholm, the TIM ( Traffic Memo ) option, the traffic reports and records if the driver was absent and off the radio. The maximum recording time was four minutes. In 1993 the combination of navigation systems to the car radio, and later they were directly integrated ( Philips CARIN (Car Information and Navigation System) ). 1997 were presented by Blaupunkt radio with DAB reception and integration of mobile phones. Even the Traffic Message Channel ( TMC) could now represent about RDS traffic information independent of the radio program on the radio display. Becker presented with the Traffic Star before an integrated combination of car radio, CD player and navigation system.

2000 to today

2001, there was a Blaupunkt car radio with MP3 decoder and MultiMediaCard slot. 2003 car radio with MP3 decoder and MultiMediaCard slot could then also record the received radio program. 2006 brought out the car radio Sony MEX- 1GP, in the control unit, enter 1 gigabyte large flash memory is integrated. The control panel can be connected via the USB cable to the PC. So you can copy it to the front panel MP3 music from your PC.

In the higher price ranges you will also find car radio with integrated DVD player. These usually come with a TFT screen with LCD technology, can be viewed on the films. A majority of these devices is provided with a navigation system. Depending on the equipment, additional screens can be connected (for example, in the rear of the vehicle). Often it is also possible, for example to connect a DVB-T receiver module or game console via an AV input.

More expensive modern car radios also have many other connection options, such as an input for a reversing system that may turn on automatically when reverse gear is engaged. In addition, increased car radio with Bluetooth interface are available that allow their functional profiles Handsfree or to access the media files from mobile phones or the like.

The previously common standard bays for car radios are now fitted only sporadically in new cars. Are usual larger devices whose dimensions and shapes vary depending on the manufacturer and model today.

Transmission paths

The transfer of shipments, both terrestrial (analogue or digital), made ​​by Internet or satellite. The latter is primarily used in North America.

Programs for car radios

For the car radio specific radio programs are broadcast. They should reach the car driving commuters during rush hour. The prime time is 6:00 to 9:00 and from 16:00 to 18:00 clock is called " Drive Time". Programs that receive a time slot during that period, can count with the highest ratings. Between the two is the amount of time the " daytime". Any shipment outside of this core program area reached only a relatively small part of the audience. During the " drive time" radio targeted programs aired. These include not only the music of the traffic, frequent time announcements or specific radio advertising such as car ads; be avoided greatly distracting or lengthy interviews. Also typical is the interval of news broadcasts, which often follow in the half hour interval. Even in the United States is the " drive time" is an important part of the daily news broadcasts, especially since it is the only time where the audience figures exceed those in the radio news of television news.

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