• CRCU: Centralized Radio Control Unit
  
• ISDN: Integrated Services Digital Network
• OFN: Optical Fibre Network
• WAN: Wide Area Network

• DRCU: Decentralized Radio Control Unit
• MRCU: Mobile Radio Control Unit
• RBS: Radio Base Station

The Centralized Radio Control Unit (CRCU) is located in the control centre. It provides the user interface for diagnostics as well as voice communication between the control centre and the vehicles via the radio network.
For voice communication the radio system provides standard ISDN interfaces for connection to a telecommunication facility. The CRCU collects diagnosis data of the radio system and visualize these messages on a diagnosis-Graphical User Interface (GUI).

The Decentralized Radio Control Unit (DRCU) controls one set of radio base stations (RBS) which are installed along the track in the radio control area. An optical fibre ring network is used to connect the RBS to the DRCU. All of the RBS are connected in a comb-like order, which means two sets of RBS are interconnected and connected to the DRCU using a different optical fibre cable to ensure highest reliability. Each decentralized radio control unit controls radio transmission of a specified part of a guide way that may consist of one or more tracks.
 
A DRCU consists of a redundant controller system. It controls its connected radio base stations which are only active if a vehicle is within the transmission range of a RBS. Each DRCU distributes and collects data from and to the RBS via its own fibre optic network.  The DRCU provides different interfaces to decentralized users.
 
For example:

• Diagnostics
• Operational voice communication
• Passenger voice communications
• Voice communication using ISDN standards
• Power propulsion system
• Decentralized control systems (interface)

Data transmission to the vehicle and vice versa is performed by the Radio Base Stations (RBS) which are allocated along the guide way according to the positioning results of the radio planning procedure. The locations are selected in a way that they ensure double radio coverage of the tracks by two system channels A and B. Each Radio Base Station is controlled by its corresponding Decentralized Radio Control Unit (DRCU). RBS and DRCU are connected with each other by the optical fibre network. An RBS is only active if a vehicle is in the vicinity of the RBS.

The low radiation of the signal is focused by bi-directional antennae along the tracks. A radio base station can supply one or more tracks. All positions of the RBS are placed along the track in a way that line of sight conditions to two adjacent RBS are provided - from each point of the track. This is a prerequisite for micro wave radio transmissions.

The Mobile Radio Control Unit (MRCU) controls the mobile part of the radio system and provides different interfaces to the mobile applications/users.

For example:

• Diagnostics
• Passenger information
• Operational voice communication
• Passenger voice communications
• Voice communication using ISDN-standards
• Location system
• Vehicle control system