Cybernetica AS Department of Navigation Systems

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Local Area Network on A-BUS

When designing a modern control and monitoring systems of aids to navigation, the modularity and openness of the system are the most important features for many customers. This means that any system could be changed by adding or taking away of equipment units without changing the whole system. It allows also building up a system gradually, step-by step in accordance with
the financial and technical resources of a customer.

The modularity and openness of EKTA’s systems are achieved by designing the system as consisting of standard hardware and software modules which can be combined in different modifications for different systems. To connect the modules together at the lights level, there is the local area RS-485 twisted pair network, or A-BUS. To this network up to 23 nodes or equipment modules  in any combination can be connected.
  • Sending  messages to other nodes and receiving messages from other nodes about current state of a node (power supply voltage under the load and standby, current consumption, statistics, logical state etc.)
  • Exchange messages with the remote control and monitoring centre through communication controller
  • Issueing commands to other nodes:
              - light ON/OFF status
              - lamp ON/OFF status
              - switch to next lamp status
              - synchronization of flashing
              - controller test
              - start Diesel engine
              - stop Diesel engine
              - clock synchronization
              - time synchronization
              - reset
  • Exchanging information with other nodes:
             - read working statistics 
             - get identification information
             - clear error status
             - get device status
             - write new flashing pattern
             - get measurement results


Physical standard of the network RS-485
Transmitter signal voltage between
“+DAT” and “-DAT”
  by sending logical “1”
  by  sending logical “0” 
+1.5 … 5V
- 1.5 … 5V
Receiver signal voltage between
“+DAT” and “-DAT”
  by  receiving logical “1”
  by receiving logical “0” 
+0.2… +7V
-0.2 … -7V
Input resistance of the receiver >12kW
Total  load of the network >54kW
Communication media twisted pair or shielded twisted pair, recommended type 24AWG  (0.2mm²) with line impedance 100…300W
Length of the line up to 1.2km, when the length exceeds 50m then using 120W  terminal resistors at both end is recommended
Number of network nodes up to 23
Data rate 9600bps
Data format start bit, 8 data bits, marker bit, 1 or more stop bits
Data coding NRZ, asynchronous, half-duplex
Addressing individual or group
Length of message from 6 bytes up to 131 bytes max.
Message package format destination address, own address, length of package, user’s data up to 126 bytes, checksum, marker


Download the A-Bus cataloge page in Adobe pdf format

If you need more information, including the information on prices and availability of our products, please do not hesitate to contact our marketing group


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© 2002 Cybernetica. Last updated 2002-10-31