CommandFusion software uses a method of data assignment and object identification called 'Joins'. Joins are basically a way of assigning a value to a particular GUI object (or multiple objects). You can think of a join as the ID of a GUI object such as a Button, Slider, etc.

Joins are divided into four data types:

1. Digital
2. Analog
3. Serial
4. List

A digital join has two possible values, 0 or 1 (off or on, low of high, active or inactive). This boolean data type allows button interaction, such as detecting button press/release and toggling the button, as well as showing/hiding subpages and performing page flips.

Within guiDesigner, digital join numbers will appear on a blue background above the object the join is assigned to when 'View > Display Object Join Numbers' is enabled.

The image below gives shows how a basic join system can work. Please note that this is just one way that joins can work.

In the system shown above, it would work as follows:

1. The inactive button with a digital join of 20 is touched
2. This sends a power toggle command, via the TCP socket to the projector
3. The projector turns on and sends feedback data via the TCP socket
4. The feedback data is processed to see if it is feedback data which relates to the power state of the projector
5. If it is, then the feedback processing you programmed into iViewer captures the power state. If the power state is high (on) then it updates any object with a digital join of 20 to active, if the power state is low (off) then is updates the button state to inactive

An analog join has an integer value ranging from 0 (zero) to 65535. This whole integer data type allows for gauge and slider interactions, such as setting a gauge level or sending a level when adjusting a slider.
It can also be used to adjust the Interval of Page Timers.

Within guiDesigner, analog join numbers will appear on a red background above the object the join is assigned to when 'View > Display Object Join Numbers' is enabled.

A serial join has a string value, with no length limitation set on the CommandFusion end (a Control System being used may have it's own string length restrictions however). This string data type allows showing dynamic text, dynamic images URLs, webview URLs, etc. A serial join value can also be set using Input Fields within iViewer.

Within guiDesigner, serial join numbers will appear on a black background above the object the join is assigned to when 'View > Display Object Join Numbers' is enabled.

A list join is used to identify a List object.

Within guiDesigner, list join numbers will appear on a red background above the object the join is assigned to when 'View > Display Object Join Numbers' is enabled.

The actual number used can be in the range from 0 to 999999999. The same join number and join type can be assigned to multiple objects in your GUI, and they will all react to a change of the join value.

A join number of zero (0) is a special case, which means “no join assigned”. By default all objects are assigned a zero join.