Car phone

A car phone is a phone that is permanently installed in a car.

• 4.1 Advantages of Fixed-mounted devices

History

The car phone represents the transition from the wired landline phone for today's mobile phone is: The connection was already over a radio link. The mobility was, however, by the size (like a travel suitcase ) and weight ( 20 kg) of the transceivers restricted; they could be transported in combination with a vehicle.

The use of car telephones was associated with high equipment costs and telephone charges. Therefore, the use in professional or even private setting could also be a status symbol.

In order at least to increase the accessibility, pagers were offered in the 1980s: A call on the car phone activated within 100 to 200 meters a beeper; the user had to return to his vehicle to answer the call.

Mobile networks in Germany

Previously focused on the mobile communication over long distances by radio almost exclusively to the police, fire and emergency medical services are available (see police radio, CB radio ). With car phones the comprehensive integration of standardized radio links in the public telephone network began, first with analog transmission technology, then digital.

→ Main article: History of mobile telephony in Germany

A network

1952 emerged the first regional city networks that aufgingen 1958 in the Federal Republic of Germany in the first public mobile phone network in the world. The devices initially weighed 16 kg and cost more than a small car ( VW Beetle ). Before hiring in 1977 could be served in the A- mains approximately 11,000 participants, the teaching was done manually by a central station, which was selected before every call.

B network

In the introduced 1972 B network for the first time it was possible to choose themselves, a mediation was no longer necessary. However, during the journey when moving to a new transmission tower was disconnected, the call had to be rebuilt. Also, the location had to be known, since each of the 158 radio areas had its own area code. The maximum number of connected nodes was 27,000. The B network was in operation until the end of 1994.

C network

With the introduction of the C - line telephony in 1985 on the frequency 450-465 MHz one was reached at a separate telephone number throughout the Federal Republic of Germany, without connection abort the change of the cell was possible. New is the option of sending faxes and data was to send at speeds of up to 14,000 bits per second and receive. As of 1989, there were for the C network, the first handsets that have been called because of their size, color and shape " briquettes " or " dog-bone". Although they were very expensive by today's standards clunky and with initially about 12,000 DM, they were ultimately the first cell phones. Even before there was already outside the car usable versions, but weighed several kilos and worn around the neck or in the form of small suitcase had been transported. The C network was in operation until the end of 2000. The highest number of participants was approximately 750,000 registered devices.

D and E networks

The digital transmission only came on with development of the D- nets in 1992. Due to the miniaturization of the devices to mobile phones car phones were increasingly unusual. However, the use of hands-free established. In 1993, parallel to the D-network e- network in operation.

Rules for making phone calls in the car

If a car phone or a hands-free system built into a car, so a tested outdoor antenna must be present amsonsten may void the type approval of the vehicle. This regulation was adopted in 2004 by the EU and implemented in 2005 by the Member States into national law.

The background is required, the relatively high transmission power of the terminal, which is formed by the shield and the body reflection and the fast movement during travel. With respect to portable devices such as cell phones, the requirement for use of an external antenna does not apply. The use of a handsfree car kit or a headset when making calls while driving, however, is dictated by the German Road Traffic Regulations:

§ 23 para 1a Highway Code ( D): " Who drives the vehicle must not use a mobile or car phone, when noted in the mobile phone or the earpiece of the car phone must be picked up or held. This does not apply if the vehicle is stopped and switched off the engine in motor vehicles. "

Today's meaning

Today, car phones usually find in conjunction with navigation systems. Fixed devices are here to compete with conventional smartphones, tablets and other portable devices. Emergency or breakdown calls are directly linked to the GPS position or other vehicle data. Moreover now the almost widespread availability of mobile Internet connections (UMTS, HSDPA and related techniques ).

Advantages of fixed built-in appliances

In the car stationary devices in comparison have a better antenna radiation (roof, rear antenna) than ordinary mobile phones. In theory, they also have a higher transmission power (up to 8 watts in D-net ). Due to the network technology advances, these differences occur but even with poor network coverage today hardly in evidence. A high transmission power can not be equated with a better link quality, but the transmit power of the terminal is greatly reduced with good link quality and thereby controlled by the base station (see transmit power control ).

Due to statutory limits no device can more effectively exploit the maximum transmit power in Germany is the maximum allowed transmission power for mobile phones at 2 watts.