APT is able to control focusers via ASCOM drivers, INDIGO / INDI as well as Meade focusers.
In order to use INDIGO / INDI is needed connection to server running on RaspberryPi, ASIAir, StarMaster, StellarMate, or Linux/MacOS computer.
For information about focusers control see the Focuser section in Gear tab.
For Meade focuser see "Meade Focuser" option in Scope & Focuser settings tab and Meade section in Gear tab.
The focuser connection is used or can be used by the following APT features: