GF82.70-P-0003RB Telephone (D-Network), Function

GF82.70-P-0003RB Telephone (D-network), Function
- with CODE (853) MB standard telephone
- with CODE (854) MB portable CTEL

Component Identification:

D-network, general
The D-network (Digital network) is made out according to the GSM standard (Global System for Mobile Communication. This allows telephone calls to countries with networks which also operate according to the GSM standard and whose users have a GSM telephone. Moreover, so-called "roaming contracts" between the countries exist to regulate telephone traffic. The countries included in these contracts are listed in so-called "roaming lists". The D-network itself has a honeycomb-type structure for the greatest possible area coverage for mobile subscribers, whereby some areas may no be covered. The individual cells have a radius of 100 m to 35 km. However, this range could be lower depending on the maximum number of calls (e.g. large cities) or due to the topographic characteristics (mountains, buildings, etc.).

Transmission problems could occur if the user is located in valleys (dead spot) or in areas with a small number of transmission and reception stations. This can, however, be eliminated by moving to another location.
Each cell has up to 16 carrier frequencies which allow up to seven conversations per carrier frequency.
Transmission of the voice and data signals is accomplished digitally in the range of 900 - 1900 MHz It allows increased security against tapping calls and provision of additional services such as:
^ Fee display
^ conference calls, waiting function
^ identification of calling party
^ call relaying

Moreover, with ISDN compatibility the D-network offers access possibilities to text and data stations (corresponding adapters required).

The D-network requires the following operating units:
^ Transmission and receiving terminal (BTS= Base Transceiver Station, per cell)
^ Concentrator (BSC=Base Station Controller, radio switching center, from the one cell to the other)
^ Switching center (MSC= Mobile Service Switching Center, from the one cell to the other)

Each transceiver station (BTS) is connected to the associated mobile service switching center (MSC) via a concentrator (BSC). The connection between the base transceiver station (BTS) and concentrator (BSC) is accomplished via radio signal (pulsed signal) and the connection from the concentrator (BSC) to the mobile service switching center (MSC) via lines (permanently-wired 4- conductor cables).

The following units are included in the mobile switching center (MSC):
^ (HLR=Home Location Register)
^ (VLR=Visitor Location Register)
^ (AC=Authentication Center)
^ (EIR=Equipment Identification Register)

In addition, the mobile service switching center (MSC) is the interface for connection to the public telephone network (PSTN, in Germany the German Telekom).
The purpose of the units listed is explained in the following examples:
^ Telephone (D-network) log-in
^ Telephone (D-network) mobile subscriber to public telephone network
^ Telephone (D-network) mobile subscriber to mobile subscriber

Each subscriber in the D-network is listed in his mobile service switching center (MSC) or the home location register (HLR) stored for him.
The network access authorization of the mobile subscriber is also checked in the authentication center (AC) located there. Moreover, defective or stolen units are identified in the equipment identification register (EIR). This leads to direct identification of the units when logged into the network.

All subscribers from other home location registers (HLR) or other networks are identified in the visitor location register (VLR)

It is possible to select between two versions:
^ Permanently installed
^ Portable CTEL