1. Termination Boards Dynamic Positioning Cabinet

2. Termination Boards Overview The termination Boards provides the connections between the field and the Process Bus. For each signal the TB also provides a fuse for the overvoltage protection. Each type of signal need a specific type of TB.

3. Types of Termination Boards There are four types of TB: TB DI ISO TB AI TB AIO DIF TBSS

4. TB DI ISO The TB DI ISO is the termination boards for the digital signals. The current loop can be powered from the card, or from an external power supply. The powering method is specific for each channel and can be configured from this board.

5. TB AI TB AI channels are normally powered from external power supplies. The internal loop power connections includes a transient voltage suppressor to protect all channels on the board from overvoltage due to excessive voltage from the power supply.

6. TB AI - Short circuit protection If an internally powered loop is short circuited, the fuses in the power lines on the termination board are blown. Consequently, all channels on that board fail. However, the power supply itself and the channels on other termination boards which are supplied from the same source are not affected.

7. TB VOTING The TB VOTING card comprises two processing stages for each of six analogue output channels. The first stage checks validity of the signal sources. If any of the sources A to C are not valid, the stage logic duplicates signals from one valid source to replace the not valid ones. This is done to ensure the best inputs for the second processing stage.

8. TB VOTING The second stage selects the median value from three inputs “A” to “C” for each individual output channel. The median value is the one having momentary value between the two others on the voltage scale. The voting comparators provide hysteresis to ensure signal stability for each output channel.

9. TB AIO DIF & TB AO V&C The TB AIO DIF card provide the necessary amplification for the output signals. If the failsafe alarm is active for some reason the card provide the appropriate “zero” signal to the thrusters. For each thruster the failsafe signal is configured on the AO V&C card.

10. TBSS The Termination Board Serial Switch (TBSS) is designed for switching serial lines to field equipment in a double- redundant computer system. It provides connectors for four serial lines from each of two Single Board Computers (SBCs) and connectors for four serial lines to field equipment.