Car phone
A car phone is a phone that is built into a car .
history
The car phone represents the transition from the wired landline phone to today's mobile phone : The connection was already made via a radio link. However, mobility was restricted by the size (comparable to a 20 liter suitcase) and weight (over 20 kg) of the transceiver equipment; they could only be transported in connection with a vehicle.
The use of car telephones was associated with high equipment costs and telephone charges. Therefore, use in a professional or even private context could also be a status symbol .
In order to at least increase accessibility, radio signal receivers were offered in the 1980s : a call on the car phone activated a beeper within a radius of 100 to 200 meters; the user had to return to their vehicle to take the call.
Cellular networks in Germany
Previously, wireless communication over long distances was almost exclusively available to the police, fire brigade and emergency medical services (see police radio , CB radio ). The widespread integration of standardized radio links into the public telephone network began with car telephones, initially with analog transmission technology, then digitally.
see main article: History of mobile telephony in Germany
A network
In 1952, the first regional city networks were created, which in 1958 in the Federal Republic of Germany were integrated into the world's first public mobile phone network. The devices initially weighed 16 kilograms and cost more than a small car ( VW Beetle ). Before the setting in 1977, approx. 11,000 subscribers could be served in the A-network, the switching was done manually by a center that was dialed before each call.
B network
In the B-network, introduced in 1972, it was possible for the first time to vote yourself; switching was no longer necessary. However, the connection was interrupted during the journey when changing to a new transmitter mast and the call had to be re-established. The whereabouts also had to be known, as each of the 158 radio areas had its own area code. The maximum number of connected participants was 27,000. The B network was in operation until the end of 1994.
C network
With the introduction of the C-Netz telephony in 1985, in the frequency range from 450 to 465 MHz, you could be reached under your own phone number throughout the Federal Republic of Germany, changing cells was possible without breaking the connection. A new feature was the ability to send and receive faxes and data at speeds of up to 14,000 bits per second. From 1989 the first handsets were available for the C-Netz, which were called "briquettes" or "dog bones" because of their size, color and shape. Although they were bulky by today's standards and very expensive at around DM 12,000 to begin with, they were ultimately the first mobile phones . Even before that, there had been versions that could be used outside of the car, but they weighed several kilograms and had to be carried around the neck or in the form of small suitcases. The C network was in operation until the end of 2000. The highest number of participants was around 750,000 registered devices.
D and E networks
The digital transmission only came on with development of the D-nets 1,992th With the miniaturization of devices into cell phones , car phones have become increasingly uncommon. However, the use of hands-free devices established itself . In 1993 the E-Netz went into operation parallel to the D-Netz.
Rules for making calls in the vehicle
If a car phone or a hands-free system is permanently installed in a car, a tested external antenna must be available, otherwise the vehicle's operating license may expire. This regulation was enacted by the EU in 2004 and implemented into national law by the member states in 2005.
The reason for this is the comparatively high transmission power required by the end device, which is caused by the shielding and reflection of the body and the rapid movement while driving. With regard to portable devices such as cell phones, the requirement to use an external antenna does not apply. The use of a hands-free system or a headset when telephoning while driving, however, is prescribed by the German road traffic regulations:
Section 23 (1a) sentence 1 StVO (D) :
“Anyone who drives a vehicle may only use an electronic device that serves or is intended to serve for communication, information or organization, if
1. the device is neither picked up nor held for this purpose and
2. either
- a) only a voice control and reading function is used or
- b) To operate and use the device, only a brief glance at the device, adapted to the road, traffic, visibility and weather conditions, while at the same time turning away from the traffic situation, is or is necessary.
Today's meaning
Today car telephones are mostly found in connection with navigation systems . Fixed devices are in competition with conventional smartphones , tablets and other portable devices. Emergency calls or breakdown calls are linked directly to the GPS position or other vehicle data . In addition, there is now almost nationwide availability of mobile Internet connections ( UMTS , HSDPA and related technologies).
Advantages of fixed devices
Devices built into the car have a better antenna radiation (roof, rear antenna) than normal cell phones. Theoretically, they also have a higher transmission power (up to 8 watts in the D network). Due to further developments in network technology, these differences hardly appear today, even with poor network coverage. A high transmission power is not to be equated with a better connection quality; rather, the transmission power of the terminal is greatly reduced if the connection quality is good and controlled by the base station (see transmission power regulation ).
Due to legal limits, no device may actually use the maximum transmission power, in Germany the maximum transmission power for cell phones is 2 watts.
Web links
Individual evidence
- ↑ History of mobile communications - 1st generation mobile communications. Website of the industry association IZMF; Retrieved November 13, 2013.
- ↑ Directive 2004/104 / EG - Official Journal of the European Union (PDF) Official law portal EU-lex of the EU. Retrieved November 13, 2013
- ↑ Technology - How do mobile radio transmission systems work? . Website of the industry association IZMF . Retrieved November 13, 2013.
- ↑ Cell phone radiation - limit values . Onmeda Internet health portal , accessed November 13, 2013