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Out Bus Element

Output signals from a subsystem as a virtual bus

  • Library:
  • Simulink / Ports & Subsystems

    Simulink / Sinks



This block has two different names, depending on the library in which it appears. The functionality of both blocks is the same.

  • In the Sinks library and the Ports & Subsystems library— Out Bus Element

  • In the Signal Routing library — Bus Element Out

To output signals in a virtual bus from a subsystem, use an Out Bus Element block for each signal in the subsystem that you want the bus to contain. This block integrates into one block the functionality of using an Outport block and a Bus Creator block. The Out Bus Element block is of the Outport block type. There are no specifications allowed on an Out Bus Element block, which supports only an inherited workflow. You cannot use the Block Parameters dialog box of an Out Bus Element block to specify bus element attributes, such as data type or dimensions.

To work with buses at subsystem interfaces, consider using In Bus Element and Out Bus Element blocks. This bus element port block combination:

  • Reduces signal line complexity and clutter in a block diagram.

  • Makes it easy to change the interface incrementally.

  • Allows access to a bus element closer to the point of usage.

    • For output, avoid a Goto, From, and Bus Creator block configuration.

    • For input, avoid a duplicate Outport blocks and a Bus Selector, Goto, and From block configuration.

To output multiple signals from a subsystem as a bus signal, create multiple Out Bus Element blocks, one for each signal.

If an Out Bus Element block creates a signal A, then another Out Bus Element block for the same port cannot specify signal A (or a child of signal A) as an element

To add a subbus, in the Block Parameters dialog box, click . To remove blocks associated with selected elements, click .

To reduce the number of bus element signals displayed in the Block Parameters dialog box, use the Filter box. The Filter box supports regular expressions. To use a regular expression character as a literal, include an escape character (\). For example, to use a question mark: sig\?1.

You can reorder bus elements by dragging and dropping a signal in the list of signals in the Block Parameters dialog box.

You can specify the background color for bus element port blocks, using the Block Parameters dialog box Set color option. This action sets the color of blocks associated with selected elements, or to all blocks if you do not select elements.


The block does not have an output port. Use the Block Parameters dialog box to specify the subsystem output port to which the block sends its input signal.


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The selected input signal is included in a bus signal that the subsystem outputs. The signal can have a real or complex values of any data type that Simulink® supports.


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Specify a name for a subsystem port. That name appears on the Subsystem and Out Bus Element block icons. If you specify a port name, that name cannot already be in use by another block or port. All Out Bus Element blocks that access the same subsystem output port reflect the port name that you specify.

Programmatic Use

Block Parameter: PortName
Type: text
Default: OutBus

Specify the order in which the port appears on the subsystem, with 1 being the top port, 2 the second port down, and so on.

  • If you specify a number that exceeds the number of subsystem output ports, new ports are added above the port associated with the Outport Bus Element block.

  • If you add an Out Bus Element block that creates another subsystem output port, the port number is the next available number.

  • If you delete all Out Bus Element blocks associated with a port, other port numbers are renumbered so that the blocks are in sequence and that no numbers are omitted.

Programmatic Use

Block Parameter: Port
Value: integer
Default: 1

Block Characteristics

Data Types

double | single | Boolean | base integer | fixed point | enumerated | bus | string

Direct Feedthrough


Multidimensional Signals


Variable-Size Signals


Zero-Crossing Detection


Extended Capabilities

Introduced in R2017a